Apparatus and method for measuring optical characteristics of an object

ABSTRACT

Optical characteristic measuring systems and methods such as for determining the color or other optical characteristics of an object are disclosed. Perimeter receiver fiber optics are spaced apart from a source fiber optic and receive light from the surface of the object being measured. Light from the perimeter fiber optics pass to a variety of filters. The system utilizes the perimeter receiver fiber optics to determine information regarding the height and angle of the probe with respect to the object being measured. Under processor control, the optical characteristics measurement may be made at a predetermined height and angle. Various color spectral photometer arrangements are disclosed. Translucency, fluorescence, gloss and/or surface texture data also may be obtained. Audio feedback may be provided to guide operator use of the system. The probe may have a removable or shielded tip for contamination prevention. A method of producing prostheses based on measured data also is disclosed. Measured data also may be stored and/or organized as part of a data base.

This is a continuation of application Ser. No. 09/462,020, filed Dec.29, 1999 U.S. Pat. No. 6,501,542 which is a 371 of PCT/US98/13764 filedJun. 30, 1998 which is a continuation of Ser. No. 08/886,223 filed Jul.1, 1997 U.S. Pat. No. 5,926,262.

FIELD OF THE INVENTION

The present invention relates to devices and methods for measuringoptical characteristics such as color spectrums, translucence, gloss,and other characteristics of objects, and more particularly to devicesand methods for measuring the color and other optical characteristics ofteeth, fabric or other objects or surfaces with a hand-held probe thatpresents minimal problems with height or angular dependencies.

BACKGROUND OF THE INVENTION

Various color/optical measuring devices such as spectrophotometers andcolorimeters are known in the art. To understand the limitations of suchconventional devices, it is helpful to understand certain principlesrelating to color. Without being bound by theory, Applicants provide thefollowing discussion.

The color of an object determines the manner in which light is reflectedfrom the object. When light is incident upon an object, the reflectedlight will vary in intensity and wavelength dependent upon the color ofthe object. Thus, a red object will reflect red light with a greaterintensity than a blue or a green object, and correspondingly a greenobject will reflect green light with a greater intensity than a red orblue object.

The optical properties of an object are also affected by the manner inwhich light is reflected from the surface. Glossy objects, those thatreflect light specularly such as mirrors or other highly polishedsurfaces, reflect light differently than diffuse objects or those thatreflect light in all directions, such as the reflection from a rough orotherwise non-polished surface. Although both objects may have the samecolor and exhibit the same reflectance or absorption optical spectralresponses, their appearances differ because of the manner in which theyreflect light.

Additionally, many objects may be translucent or have semi-translucentsurfaces or thin layers covering their surfaces. For example, somematerials have a complicated structure consisting of an outer layer andan inner layer. The outer layer is semitranslucent. The inner layers arealso translucent to a greater or lesser degree. Such materials andobjects also appear different from objects that are opaque, even thoughthey may be the same color because of the manner in which they canpropagate light in the translucent layer and emit the light raydisplaced from its point of entry.

One method of quantifying the color of an object is to illuminate itwith broad band spectrum or “white” light, and measure the spectralproperties of the reflected light over the entire visible spectrum andcompare the reflected spectrum with the incident light spectrum. Suchinstruments typically require a broad band spectrophotometer, whichgenerally are expensive, bulky and relatively cumbersome to operate,thereby limiting the practical application of such instruments.

For certain applications, the broad band data provided by aspectrophotometer is unnecessary. For such applications, devices havebeen produced or proposed that quantify color in terms of a numericalvalue or relatively small set of values representative of the color ofthe object.

It is known that the color of an object can be represented by threevalues. For example, the color of an object can be represented by red,green and blue values, an intensity value and color difference values,by a CIE value, or by what are known as “tristimulus values” or numerousother orthogonal combinations. For most tristimulus systems, the threevalues are orthogonal; i.e., any combination of two elements in the setcannot be included in the third element.

One such method of quantifying the color of an object is to illuminatean object with broad band “white” light and measure the intensity of thereflected light after it has been passed through narrow band filters.Typically three filters (such as red, green and blue) are used toprovide tristimulus light values representative of the color of thesurface. Yet another method is to illuminate an object with threemonochromatic light sources or narrow band light sources (such as red,green and blue) one at a time and then measure the intensity of thereflected light with a single light sensor. The three measurements arethen converted to a tristimulus value representative of the color of thesurface. Such color measurement techniques can be utilized to produceequivalent tristimulus values representative of the color of thesurface. Generally, it does not matter if a “white” light source is usedwith a plurality of color sensors (or a continuum in the case of aspectrophotometer), or if a plurality of colored light sources areutilized with a single light sensor.

There are, however, difficulties with the conventional techniques. Whenlight is incident upon a surface and reflected to a light receiver, theheight of the light sensor and the angle of the sensor relative to thesurface and to the light source also affect the intensity of thereceived light. Since the color determination is being made by measuringand quantifying the intensity of the received light for differentcolors, it is important that the height and angular dependency of thelight receiver be eliminated or accounted for in some manner.

One method for eliminating the height and angular dependency of thelight source and receiver is to provide a fixed mounting arrangementwhere the light source and receiver are stationary and the object isalways positioned and measured at a preset height and angle. The fixedmounting arrangement greatly limits the applicability of such a method.Another method is to add mounting feet to the light source and receiverprobe and to touch the object with the probe to maintain a constantheight and angle. The feet in such an apparatus must be wide enoughapart to insure that a constant angle (usually perpendicular) ismaintained relative to the object. Such an apparatus tends to be verydifficult to utilize on small objects or on objects that are hard toreach, and in general does not work satisfactorily in measuring objectswith curved surfaces.

The use of color measuring devices in the field of dentistry has beenproposed. In modern dentistry, the color of teeth typically arequantified by manually comparing a patient's teeth with a set of “shadeguides.” There are numerous shade guides available for dentists in orderto properly select the desired color of dental prosthesis. Such shadeguides have been utilized for decades and the color determination ismade subjectively by the dentist by holding a set of shade guides nextto a patient's teeth and attempting to find the best match.Unfortunately, however, the best match often is affected by the ambientlight color in the dental operatory and the surrounding color of thepatient's makeup or clothing and by the fatigue level of the dentist.

Similar subjective color quantification also is made in the paintindustry by comparing the color of an object with a paint referenceguide. There are numerous paint guides available in the industry and thecolor determination also often is affected by ambient light color, userfatigue and the color sensitivity of the user. Many individuals arecolor insensitive (color blind) to certain colors, further complicatingcolor determination.

In general, color quantification is needed in many industries. Several,but certainly not all, applications include: dentistry (color of teeth);dermatology (color of skin lesions); interior decorating (color ofpaint, fabrics); the textile industry; automotive repair (matching paintcolors); photography (color of reproductions, color reference ofphotographs to the object being photographed); printing and lithography;cosmetics (hair and skin color, makeup matching); and other applicationsin which it useful to measure color in an expedient and reliable manner.

With respect to such applications, however, the limitations ofconventional color/optical measuring techniques typically restrict theutility of such techniques. For example, the high cost and bulkiness oftypical broad band spectrometers, and the fixed mounting arrangements orfeet required to address the height and angular dependency, often limitthe applicability of such conventional techniques.

Moreover, another limitation of such conventional methods and devicesare that the resolution of the height and angular dependency problemstypically require contact with the object being measured. In certainapplications, it may be desirable to measure and quantify the color ofan object with a small probe that does not require contact with thesurface of the object. In certain applications, for example, hygienicconsiderations make such contact undesirable. In the other applicationssuch as interior decorating, contact with the object can mar the surface(such as if the object is coated with wet paint) or otherwise causeundesirable effects.

In summary, there is a need for a low cost, hand-held probe of smallsize that can reliably measure and quantify the color and other opticalcharacteristics of an object without requiring physical contact with theobject, and also a need for methods based on such a device in the fieldto dentistry and other applications.

SUMMARY OF THE INVENTION

In accordance with the present invention, devices and methods areprovided for measuring the color and other optical characteristics ofobjects, reliably and with minimal problems of height and angulardependence. A handheld probe is utilized in the present invention, withthe handheld probe containing a number of fiber optics in certainpreferred embodiments. Light is directed from one (or more) lightsource(s) towards the object to be measured, which in certain preferredembodiments is a central light source fiber optic (other light sourcesand light source arrangements also may be utilized). Light reflectedfrom the object is detected by a number of light receivers. Included inthe light receivers (which may be light receiver fiber optics) are aplurality of perimeter and/or broadband or other receivers (which may bereceiver fiber optics, etc.). In certain preferred embodiments, a numberof groups of perimeter fiber optics are utilized in order to takemeasurements at a desired, and predetermined height and angle, therebyminimizing height and angular dependency problems found in conventionalmethods, and to quantify other optical characteristics such as gloss. Incertain embodiments, the present invention also may measure gloss,translucence, and fluorescence characteristics of the object beingmeasured, as well as surface texture and/or other optical or surfacecharacteristics. In certain embodiments, the present invention maydistinguish the surface spectral reflectance response and also a bulkspectral response.

The present invention may include constituent elements of a broad bandspectrophotometer, or, alternatively, may include constituent elementsof a tristimulus type calorimeter. The present invention may employ avariety of color measuring devices in order to measure color and otheroptical characteristics in a practical, reliable and efficient manner,and in certain preferred embodiments includes a color filter array and aplurality of color sensors. A microprocessor is included for control andcalculation purposes. A temperature sensor is included to measuretemperature in order to detect abnormal conditions and/or to compensatefor temperature effects of the filters or other components of thesystem. In addition, the present invention may include audio feedback toguide the operator in making color/optical measurements, as well as oneor more display devices for displaying control, status or otherinformation.

With the present invention, color/optical measurements may be made witha handheld probe in a practical and reliable manner, essentially free ofheight and angular dependency problems, without resorting to fixtures,feet or other undesirable mechanical arrangements for fixing the heightand angle of the probe with respect to the object.

Accordingly, it is an object of the present invention to addresslimitations of conventional color/optical measuring techniques.

It is another object of the present invention to provide a method anddevice useful in measuring the color or other optical characteristics ofteeth, fabric or other objects or surfaces with a hand-held probe ofpractical size that may advantageously utilize, but does not necessarilyrequire, contact with the object or surface.

It is a further object of the present invention to provide acolor/optical measurement probe and method that does not require fixedposition mechanical mounting, feet or other mechanical impediments.

It is yet another object of the present invention to provide a probe andmethod useful for measuring color and/or other optical characteristicsthat may be utilized with a probe simply placed near the surface to bemeasured.

It is a still further object of the present invention to provide a probeand method that are capable of determining translucency characteristicsof the object being measured.

It is still further object of the present invention to provide a probeand method that are capable of determining translucency characteristicsof the object being measured by making measurements from one side of theobject.

It is a further object of the present invention to provide a probe andmethod that are capable of determining surface texture characteristicsof the object being measured.

It is a still further object of the present invention to provide a probeand method that are capable of determining fluorescence characteristicsof the object being measured.

It is yet a further object of the present invention to provide a probeand method that are capable of determining gloss (or degree of specularreflectance) characteristics of the object being measured.

It is another object of the present invention to provide a probe andmethod that can measure the area of a small spot singularly, or thatalso can measure irregular shapes by moving the probe over an area andintegrating the color of the entire area.

It is a further object of the present invention to provide a method ofmeasuring the color of an object and preparing prostheses, coloredfillings, or other materials or taking other action.

It is yet another object of the present invention to provide a methodand apparatus that minimizes contamination problems, while providing areliable and expedient manner in which to measure an object and preparecoatings, layers, prostheses, colored fillings, or other materials.expedient manner in which to measure an object and prepare coatings,layers, prostheses, colored fillings, or other materials.

It is an object of the present invention to provide methods of usingmeasured data to implement processes for forming objects, prostheses andthe like, as well as methods for keeping such measurement and/or otherdata as part of a record database.

It also is an object of the present invention to provide probes andmethods for measuring optical characteristics with a probe that is heldsubstantially stationary with respect to the object being measured.

Finally, it is an object of the present invention to provide probes andmethods for measuring optical characteristics with a probe that may havea removable tip or shield that may be removed for cleaning, disposedafter use or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may be more fully understood by a description ofcertain preferred embodiments in conjunction with the attached drawingsin which:

FIG. 1 is a diagram illustrating a preferred embodiment of the presentinvention;

FIG. 2 is a diagram illustrating a cross section of a probe that may beused in accordance with a certain embodiments of the present invention;

FIG. 3 is a diagram illustrating an illustrative arrangement of fiberoptic receivers and sensors utilized with a certain embodiments;

FIGS. 4A to 4C illustrate certain geometric considerations of fiberoptics;

FIGS. 5A and 5B illustrate the light amplitude received by fiber opticlight receivers as the receivers are moved towards and away from anobject;

FIG. 6 is a flow chart illustrating a color measuring method inaccordance with an embodiment of the present invention;

FIGS. 7A and 7B illustrate a protective cap that may be used withcertain embodiments of the present invention;

FIGS. 8A and 8B illustrate removable probe tips that may be used withcertain embodiments of the present invention;

FIG. 9 illustrates a fiber optic bundle in accordance with anotherembodiment, which may serve to further the understanding of preferredembodiments of the present invention;

FIGS. 10A, 10B, 10C, and 10D illustrate and describe other fiber opticbundle configurations and principles, which may serve to further theunderstanding of preferred embodiments of the present invention;

FIG. 11 illustrates a linear optical sensor array that may be used incertain embodiments of the present invention;

FIG. 12 illustrates a matrix optical sensor array that may be used incertain embodiments of the present invention;

FIGS. 13A and 13B illustrate certain optical properties of a filterarray that may be used in certain embodiments of the present invention;

FIGS. 14A and 14B illustrate examples of received light intensities ofreceivers used in certain embodiments of the present invention;

FIG. 15 is a flow chart illustrating audio tones that may be used incertain embodiments of the present invention;

FIG. 16 illustrates an embodiment, which utilizes a plurality of ringsof light receivers that may be utilized to take measurements with theprobe held substantially stationary with respect to the object beingmeasured, which may serve to further the understanding of preferredembodiments of the present invention;

FIGS. 17 and 18 illustrate an embodiment, which utilizes a mechanicalmovement and also may be utilized to take measurements with the probeheld substantially stationary with respect to the object being measured,which may serve to further the understanding of preferred embodiments ofthe present invention;

FIGS. 19A to 19C illustrate embodiments of the present invention inwhich coherent light conduits may serve as removable probe tips;

FIGS. 20A and 20B illustrate cross sections of probes that may be usedin accordance with preferred embodiments of the present invention;

FIGS. 21 and 22A and 22B illustrate certain geometric and otherproperties of fiber optics for purposes of understanding certainpreferred embodiments;

FIGS. 23A and 23B illustrate probes for measuring “specular-excluded”type spectrums in accordance with the present invention;

FIGS. 24, 25, and 26 illustrate embodiments in which cameras andreflectometer type instruments in accordance with the present inventionare integrated.

FIGS. 27 and 28 illustrate certain handheld embodiments of the presentinvention; and

FIG. 29 illustrates an object in cross section, illustrating howembodiments of the present invention may be used to assess subsurfacecharacteristics of various types of objects; and

FIGS. 30 to 42 illustrate other embodiments (systems, sources,receivers, etc.), aspects and features within the scope of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in greater detail with referenceto certain preferred embodiments and certain other embodiments, whichmay serve to further the understanding of preferred embodiments of thepresent invention. As described elsewhere herein, various refinementsand substitutions of the various embodiments are possible based on theprinciples and teachings herein.

With reference to FIG. 1, an exemplary preferred embodiment of acolor/optical characteristic measuring system and method in accordancewith the present invention will be described.

Probe tip 1 encloses a plurality of fiber optics, each of which mayconstitute one or more fiber optic fibers. In a preferred embodiment,the fiber optics contained within probe tip 1 includes a single lightsource fiber optic and a number of groups of light receiver fiberoptics. The use of such fiber optics to measure the color or otheroptical characteristics of an object will be described later herein.Probe tip 1 is attached to probe body 2, on which is fixed switch 17.Switch 17 communicates with microprocessor 10 through wire 18 andprovides, for example, a mechanism by which an operator may activate thedevice in order to make a color/optical measurement. Fiber optics withinprobe tip 1 terminate at the forward end thereof (i.e., the end awayfrom probe body 2). The forward end of probe tip 1 is directed towardsthe surface of the object to be measured as described more fully below.The fiber optics within probe tip 1 optically extend through probe body2 and through fiber optic cable 3 to light sensors 8, which are coupledto microprocessor 10.

It should be noted that microprocessor 10 includes conventionalassociated components, such as memory (programmable memory, such asPROM, EPROM or EEPROM; working memory such as DRAMs or SRAMS; and/orother types of memory such as non-volatile memory, such as FLASH),peripheral circuits, clocks and power supplies, although for claritysuch components are not explicitly shown. Other types of computingdevices (such as other microprocessor systems, programmable logic arraysor the like) are used in other embodiments of the present invention.

In the embodiment of FIG. 1, the fiber optics from fiber optic cable 3end at splicing connector 4. From splicing connector 4, each or some ofthe receiver fiber optics used in this embodiment is/are spliced into anumber of smaller fiber optics (generally denoted as fibers 7), which inthis embodiment are fibers of equal diameter, but which in otherpreferred embodiments may be of unequal diameter and/or numeric aperture(NA) (including, for example, larger or smaller “height/angle” orperimeter fibers, as more fully described herein). One of the fibers ofeach group of fibers may pass to light sensors 8 through a neutraldensity filter (as more fully described with reference to FIG. 3), andcollectively such neutrally filtered fibers may be utilized for purposesof height/angle determination, translucency determination, and glossdetermination (and also may be utilized to measure other surfacecharacteristics, as more fully described herein). Remaining fibers ofeach group of fibers may pass to light sensors 8 through color filtersand may be used to make color/optical measurements. In still otherembodiments, splicing connector 4 is not used, and fiber bundles of, forexample, five or more fibers each extend from light sensors 8 to theforward end of probe tip 1. In certain embodiments, unused fibers orother materials may be included as part of a bundle of fibers forpurposes of, for example, easing the manufacturing process for the fiberbundle. What should be noted is that, for purposes of the presentinvention, a plurality of light receiver fiber optics or elements (suchas fibers 7) are presented to light sensors 8, with the light from thelight receiver fiber optics/elements representing light reflected fromobject 20. While the various embodiments described herein presenttradeoffs and benefits that may not have been apparent prior to thepresent invention (and thus may be independently novel), what isimportant for the present discussion is that light from fiberoptics/elements at the forward end of probe tip 1 is presented tosensors 8 for color/optical measurements and angle/height determination,etc. In particular, fiber optic configurations of certain preferredembodiments will be explained in more detail hereinafter.

Light source 11 in the preferred embodiment is a halogen light source(of, for example, 5-100 watts, with the particular wattage chosen forthe particular application), which may be under the control ofmicroprocessor 10. The light from light source 11 reflects from coldmirror 6 and into source fiber optic 5. Source fiber optic 5 passesthrough to the forward end of probe tip 1 and provides the lightstimulus used for purposes of making the measurements described herein.Cold mirror 6 reflects visible light and passes infra-red light, and isused to reduce the amount of infra-red light produced by light source 11before the light is introduced into source fiber optic 5. Such infra-redlight reduction of the light from a halogen source such as light source11 can help prevent saturation of the receiving light sensors, which canreduce overall system sensitivity. Fiber 15 receives light directly fromlight source 11 and passes through to light sensors 8 (which may bethrough a neutral density filter). Microprocessor 10 monitors the lightoutput of light source 11 through fiber 15, and thus may monitor and, ifnecessary compensate for, drift of the output of light source 11. Incertain embodiments, microprocessor 10 also may sound an alarm (such asthrough speaker 16) or otherwise provide some indication if abnormal orother undesired performance of light source 11 is detected.

The data output from light sensors 8 pass to microprocessor 10.Microprocessor 10 processes the data from light sensors 8 to produce ameasurement of color and/or other characteristics. Microprocessor 10also is coupled to key pad switches 12, which serve as an input device.Through key pad switches 12, the operator may input control informationor commands, or information relating to the object being measured or thelike. In general, key pad switches 12, or other suitable data inputdevices (such as push button, toggle, membrane or other switches or thelike), serve as a mechanism to input desired information tomicroprocessor 10.

Microprocessor 10 also communicates with UART 13, which enablesmicroprocessor 10 to be coupled to an external device such as computer13A. In such embodiments, data provided by microprocessor 10 may beprocessed as desired for the particular application, such as foraveraging, format conversion or for various display or print options,etc. In the preferred embodiment, UART 13 is configured so as to providewhat is known as a RS232 interface, such as is commonly found inpersonal computers.

Microprocessor 10 also communicates with LCD 14 for purposes ofdisplaying status, control or other information as desired for theparticular application. For example, color bars, charts or other graphicrepresentations of the color or other collected data and/or the measuredobject may be displayed. In other embodiments, other display devices areused, such as CRTs, matrix-type LEDs, lights or other mechanisms forproducing a visible indicia of system status or the like. Upon systeminitialization, for example, LCD 14 may provide an indication that thesystem is stable, ready and available for taking color measurements.

Also coupled to microprocessor 10 is speaker 16. Speaker 16, in apreferred embodiment as discussed more fully below, serves to provideaudio feedback to the operator, which may serve to guide the operator inthe use of the device. Speaker 16 also may serve to provide status orother information alerting the operator of the condition of the system,including an audio tone, beeps or other audible indication (i.e., voice)that the system is initialized and available for taking measurements.Speaker 16 also may present audio information indicative of the measureddata, shade guide or reference values corresponding to the measureddata, or an indication of the status of the color/optical measurements.

Microprocessor 10 also receives an input from temperature sensor 9.Given that many types of filters (and perhaps light sources or othercomponents) may operate reliably only in a given temperature range,temperature sensor 9 serves to provide temperature information tomicroprocessor 10. In particular, color filters, such as may be includedin light sensors 8, may be sensitive to temperature, and may operatereliably only over a certain temperature range. In certain embodiments,if the temperature is within a usable range, microprocessor 10 maycompensate for temperature variations of the color filters. In suchembodiments, the color filters are characterized as to filteringcharacteristics as a function of temperature, either by data provided bythe filter manufacturer, or through measurement as a function oftemperature. Such filter temperature compensation data may be stored inthe form of a look-up table in memory, or may be stored as a set ofpolynomial coefficients from which the temperature characteristics ofthe filters may be computed by microprocessor 10.

In general, under control of microprocessor 10, which may be in responseto operator activation (through, for example, key pad switches 12 orswitch 17), light is directed from light source 11, and reflected fromcold mirror 6 through source fiber optic 5 (and through fiber opticcable 3, probe body 2 and probe tip 1, or through some other suitablelight source element) and is directed onto object 20. Light reflectedfrom object 20 passes through the receiver fiber optics/elements inprobe tip 1 to light sensors 8 (through probe body 2, fiber optic cable3 and fibers 7). Based on the information produced by light sensors 8,microprocessor 10 produces a color/optical measurement result or otherinformation to the operator. Color measurement or other data produced bymicroprocessor 10 may be displayed on display 14, passed through UART 13to computer 13A, or used to generate audio information that is presentedto speaker 16. Other operational aspects of the preferred embodimentillustrated in FIG. 1 will be explained hereinafter.

With reference to FIG. 2, an embodiment of a fiber optic arrangementpresented at the forward end of probe tip 1 will now be described, whichmay serve to further the understanding of preferred embodiments of thepresent invention. As illustrated in FIG. 2, this embodiment utilizes asingle central light source fiber optic, denoted as light source fiberoptic S, and a plurality of perimeter light receiver fiber optics,denoted as light receivers R1, R2 and R3. As is illustrated, thisembodiment utilizes three perimeter fiber optics, although in otherembodiments two, four or some other number of receiver fiber optics areutilized. As more fully described herein, the perimeter light receiverfiber optics serve not only to provide reflected light for purposes ofmaking the color/optical measurement, but such perimeter fibers alsoserve to provide information regarding the angle and height of probe tip1 with respect to the surface of the object that is being measured, andalso may provide information regarding the surface characteristics ofthe object that is being measured.

In the illustrated embodiment, receiver fiber optics R1 to R3 arepositioned symmetrically around source fiber optic S, with a spacing ofabout 120 degrees from each other. It should be noted that spacing t isprovided between receiver fiber optics R1 to R3 and source fiber opticS. While the precise angular placement of the receiver fiber opticsaround the perimeter of the fiber bundle in general is not critical, ithas been determined that three receiver fiber optics positioned 120degrees apart generally may give acceptable results. As discussed above,in certain embodiments light receiver fiber optics R1 to R3 eachconstitute a single fiber, which is divided at splicing connector 4(refer again to FIG. 1), or, in alternate embodiments, light receiverfiber optics R1 to R3 each constitute a bundle of fibers, numbering, forexample, at least five fibers per bundle. It has been determined that,with available fibers of uniform size, a bundle of, for example, sevenfibers may be readily produced (although as will be apparent to one ofskill in the art, the precise number of fibers may be determined in viewof the desired number of receiver fiber optics, manufacturingconsiderations, etc.). The use of light receiver fiber optics R1 to R3to produce color/optical measurements is further described elsewhereherein, although it may be noted here that receiver fiber optics R1 toR3 may serve to detect whether, for example, the angle of probe tip 1with respect to the surface of the object being measured is at 90degrees, or if the surface of the object being measured contains surfacetexture and/or spectral irregularities. In the case where probe tip 1 isperpendicular to the surface of the object being measured and thesurface of the object being measured is a diffuse reflector (i.e., amatte-type reflector, as compared to a glossy, spectral, or shiny-typereflector which may have “hot spots”), then the light intensity inputinto the perimeter fibers should be approximately equal. It also shouldbe noted that spacing t serves to adjust the optimal height at whichcolor/optical measurements should be made (as more fully describedbelow). Preferred embodiments, as described hereinafter, may enable thequantification of the gloss or degree of spectral reflection of theobject being measured.

In one particular aspect useful with embodiments of the presentinvention, area between the fiber optics on probe tip 1 may be wholly orpartially filled with a non-reflective material and/or surface (whichmay be a black mat, contoured or other non-reflective surface). Havingsuch exposed area of probe tip 1 non-reflective helps to reduceundesired reflections, thereby helping to increase the accuracy andreliability.

With reference to FIG. 3, a partial arrangement of light receiver fiberoptics and sensors that may be used in a preferred embodiment of thepresent invention will now be described. Fibers 7 represent lightreceiving fiber optics, which transmit light reflected from the objectbeing measured to light sensors 8. In an exemplary embodiment, sixteensensors (two sets of eight) are utilized, although for ease ofdiscussion only 8 are illustrated in FIG. 3 (in this preferredembodiment, the circuitry of FIG. 3 is duplicated, for example, in orderto result in sixteen sensors). In other embodiments, other numbers ofsensors are utilized in accordance with the present invention.

Light from fibers 7 is presented to sensors 8, which in a preferredembodiment pass through filters 22 to sensing elements 24. In thispreferred embodiment, sensing elements 24 include light-to-frequencyconverters, manufactured by Texas Instruments and sold under the partnumber TSL230. Such converters constitute, in general, photo diodearrays that integrate the light received from fibers 7 and output an ACsignal with a frequency proportional to the intensity (not frequency) ofthe incident light. Without being bound by theory, the basic principleof such devices is that, as the intensity increases, the integratoroutput voltage rises more quickly, and the shorter the integrator risetime, the greater the output frequency. The outputs of the TSL230sensors are TTL compatible digital signals, which may be coupled tovarious digital logic devices.

The outputs of sensing elements 24 are, in this embodiment, asynchronoussignals of frequencies depending upon the light intensity presented tothe particular sensing elements, which are presented to processor 26. Ina preferred embodiment, processor 26 is a Microchip PIC16C55 or PIC16C57microprocessor, which as described more fully herein implements analgorithm to measure the frequencies of the signals output by sensingelements 24. In other embodiments, a more integratedmicroprocessor/microcontroller, such as Hitachi's SH RISCmicrocontrollers, is utilized to provide further system integration orthe like.

As previously described, processor 26 measures the frequencies of thesignals output from sensing elements 24. In a preferred embodiment,processor 26 implements a software timing loop, and at periodicintervals processor 26 reads the states of the outputs of sensingelements 24. An internal counter is incremented each pass through thesoftware timing loop. The accuracy of the timing loop generally isdetermined by the crystal oscillator time base (not shown in FIG. 3)coupled to processor 26 (such oscillators typically are quite stable).After reading the outputs of sensing elements 24, processor 26 performsan exclusive OR (“XOR”) operation with the last data read (in apreferred embodiment such data is read in byte length). If any bit haschanged, the XOR operation will produce a 1, and, if no bits havechanged, the XOR operation will produce a 0. If the result is non-zero,the input byte is saved along with the value of the internal counter(that is incremented each pass through the software timing loop). If theresult is zero, the systems waits (e.g., executes no operationinstructions) the same amount of time as if the data had to be saved,and the looping operation continues. The process continues until alleight inputs have changed at least twice, which enables measurement of afull ½ period of each input. Upon conclusion of the looping processprocessor 26 analyzes the stored input bytes and internal counterstates. There should be 2 to 16 saved inputs (for the 8 total sensors ofFIG. 3) and counter states (if two or more inputs change at the sametime, they are saved simultaneously). As will be understood by one ofskill in the art, the stored values of the internal counter containsinformation determinative of the period of the signals received fromsensing elements 24. By proper subtraction of internal counter values attimes when an input bit has changed, the period may be calculated. Suchperiods calculated for each of the outputs of sensing elements isprovided by processor 26 to microprocessor 10 (see, e.g., FIG. 1). Fromsuch calculated periods, a measure of the received light intensities maybe calculated. In alternate embodiments, the frequency of the outputs ofthe TSL230 sensors is measured directly by a similar software loop asthe one described above. The outputs are monitored by the RISC processorin a software timing loop and are XORed with the previous input asdescribed above. If a transition occurs for a particular TSL230 input, acounter register for the particular TSL230 input is incremented. Thesoftware loop is executed for a pre-determined period of time and thefrequency of the input is calculated by dividing the number oftransitions by the predetermined time and scaling the result. It willalso be apparent to one skilled in the art that more sophisticatedmeasurement schemes can also be implemented whereby both the frequencyand period are simultaneously measured by high speed RISC processorssuch as those of the Hitachi SH family.

It should be noted that the sensing circuitry and methodologyillustrated in FIG. 3 have been determined to provide a practical andexpedient manner in which to measure the light intensities received bysensing elements 24. In other embodiments, other circuits andmethodologies are employed (such other exemplary sensing schemes aredescribed elsewhere herein).

As discussed above with reference to FIG. 1, one or more of fibers 7measures light source 11, which may be through a neutral density filter,which serves to reduce the intensity of the received light in order tomaintain the intensity roughly in the range of the other received lightintensities. A number of fibers 7 also are from perimeter receiver fiberoptics R1 to R3 (see, e.g., FIG. 2) and also may pass through neutraldensity filters. Such receiving fibers 7 serve to provide data fromwhich angle/height information and/or surface characteristics may bedetermined.

The remaining twelve fibers (of the illustrated embodiment's total of 16fibers) of fibers 7 pass through color filters and are used to producethe color measurement. In an embodiment, the color filters are KodakSharp Cutting Wratten Gelatin Filters which pass light with wavelengthsgreater than the cut-off value of the filter (i.e., redish values), andabsorb light with wavelengths less than the cut-off value of the filter(i.e., bluish values). “Sharp Cutting” filters are available in a widevariety of cut-off frequencies/wavelengths, and the cut-off valuesgenerally may be selected by proper selection of the desired cut-offfilter. In an embodiment, the filter cut-off values are chosen to coverthe entire visible spectrum and, in general, to have band spacings ofapproximately the visible band range (or other desired range) divided bythe number of receivers/filters. As an example, 700 nanometers minus 400nanometers, divided by 11 bands (produced by twelve colorreceivers/sensors), is roughly 30 nanometer band spacing.

With an array of cut-off filters as described above, and without beingbound by theory or the specific embodiments described herein, thereceived optical spectrum may be measured/calculated by subtracting thelight intensities of “adjacent” color receivers. For example, band 1(400 nm to 430 nm)=(intensity of receiver 12) minus (intensity ofreceiver 11), and so on for the remaining bands. Such an array ofcut-off filters, and the intensity values that may result from filteringwith such an array, are more fully described in connection with FIGS.13A to 14B.

It should be noted here that in alternate embodiments other color filterarrangements are utilized. For example, “notch” or bandpass filters maybe utilized, such as may be developed using Schott glass-type filters(whether constructed from separate longpass/shortpass filters orotherwise) or notch interference filters such as those manufactured byCorion, etc.

In a preferred embodiment of the present invention, the specificcharacteristics of the light source, filters, sensors and fiber optics,etc., are normalized/calibrated by directing the probe towards, andmeasuring, a known color standard. Such normalization/calibration may beperformed by placing the probe in a suitable fixture, with the probedirected from a predetermined position (i.e., height and angle) from theknown color standard. Such measured normalization/calibration data maybe stored, for example, in a look-up table, and used by microprocessor10 to normalize or correct measured color or other data. Such proceduresmay be conducted at start-up, at regular periodic intervals, or byoperator command, etc. In particular embodiments, a large number ofmeasurements may be taken on materials of particular characteristics andprocessed and/or statistically analyzed or the like, with datarepresenting or derived from such measurements stored in memory (such asa look-up table or polynomial or other coefficients, etc.). Thereafter,based upon measurements of an object taken in accordance with thepresent invention, comparisons may be made with the stored data andassessments of the measured object made or predicted. In oneillustrative example, an assessment or prediction may be made of whetherthe object is wet or dry (having water or other liquid on its surface,wet paint, etc.) based on measurements in accordance with the presentinvention. In yet another illustrative example, an assessment orprediction of the characteristics of an underlying material, such astissue before the surface of a tooth, skin, or other material. Suchcapabilities may be further enhanced by comparisons with measurement'staken of the object at an earlier time, such as data taken of the objectat one or more earlier points in time. Such comparisons based on suchhistorical data and/or stored data may allow highly useful assessmentsor predictions of the current or projected condition or status of thetooth, tissue, or other object, etc. Many other industrial uses of suchsurface and subsurface assessment/prediction capabilities are possible.

What should be noted from the above description is that the receivingand sensing fiber optics and circuitry illustrated in FIG. 3 provide apractical and expedient way to determine the color and other optical orother characteristics by measuring the intensity of the light reflectedfrom the surface of the object being measured.

It also should be noted that such a system measures the spectral band ofthe reflected light from the object, and once measured such spectraldata may be utilized in a variety of ways. For example, such spectraldata may be displayed directly as intensity-wavelength band values. Inaddition, tristimulus type values may be readily computed (through, forexample, conventional matrix math), as may any other desired colorvalues. In one particular embodiment useful in dental applications (suchas for dental prostheses), the color data is output in the form of aclosest match or matches of dental shade guide value(s). In a preferredembodiment, various existing shade guides (such as the shade guidesproduced by Vita Zahnfabrik) are characterized and stored in a look-uptable, or in the graphics art industry Pantone color references, and thecolor measurement data are used to select the closest shade guide valueor values, which may be accompanied by a confidence level or othersuitable factor indicating the degree of closeness of the match ormatches, including, for example, what are known as ΔE values or rangesof ΔE values, or criteria based on standard deviations, such as standarddeviation minimization. In still other embodiments, the colormeasurement data are used (such as with look-up tables) to selectmaterials for the composition of paint or ceramics such as forprosthetic teeth. There are many other uses of such spectral datameasured in accordance with the present invention.

It is known that certain objects such as human teeth may fluoresce, andsuch optical characteristics also may be measured in accordance with thepresent invention. A light source with an ultraviolet component may beused to produce more accurate color/optical data with respect to suchobjects. Such data may be utilized to adjust the amounts and orproportions or types of fluorescing materials in layers, coatings,restorations or prosthesis, etc. In certain embodiments, atungsten/halogen source (such as used in a preferred embodiment) may becombined with a UV light source (such as a mercury vapor, xenon or otherfluorescent light source, etc.) to produce a light output capable ofcausing the object to fluoresce. Alternately, a separate UV lightsource, combined with a visible-light-blocking filter, may be used toilluminate the object. Such a UV light source may be combined with lightfrom a red LED (for example) in order to provide a visual indication ofwhen the UV light is on and also to serve as an aid for the directionalpositioning of the probe operating with such a light source. A secondmeasurement may be taken using the UV light source in a manner analogousto that described earlier, with the band of the red LED or othersupplemental light source being ignored. The second measurement may thusbe used to produce an indication of the fluorescence of the object beingmeasured. With such a UV light source, a silica fiber optic (or othersuitable material) typically would be required to transmit the light tothe object (standard fiber optic materials such as glass and plastic ingeneral do not propagate UV light in a desired manner, etc.).

As described earlier, in certain preferred embodiments the presentinvention utilizes a plurality of perimeter receiver fiber optics spacedapart from and around a central source fiber optic to measure color anddetermine information regarding the height and angle of the probe withrespect to the surface of the object being measured, which may includeother surface characteristic information, etc. Without being bound bytheory, certain principles underlying certain aspects of the presentinvention will now be described with reference to FIGS. 4A to 4C.

FIG. 4A illustrates a typical step index fiber optic consisting of acore and a cladding. For this discussion, it is assumed that the corehas an index of refraction of n₀ and the cladding has an index ofrefraction of n₁. Although the following discussion is directed to “stepindex” fibers, it will be appreciated by those of skill in the art thatsuch discussion generally is applicable for gradient index fibers aswell.

In order to propagate light without loss, the light must be incidentwithin the core of the fiber optic at an angle greater than the criticalangle, which may be represented as Sin⁻¹{n₁/n₀}, where n₀ is the indexof refraction of the core and n₁ is the index of refraction of thecladding. Thus, all light must enter the fiber at an acceptance angleequal to or less than phi, with phi=2×Sin⁻¹{√(n₀ ²−n₁ ²)}, or it willnot be propagated in a desired manner.

For light entering a fiber optic, it must enter within the acceptanceangle phi. Similarly, when the light exits a fiber optic, it will exitthe fiber optic within a cone of angle phi as illustrated in FIG. 4A.The value √(n₀ ²−n₁ ²) is referred to as the aperture of the fiberoptic. For example, a typical fiber optic may have an aperture of 0.5,and an acceptance angle of 60°.

Consider using a fiber optic as a light source. One end is illuminatedby a light source (such as light source 11 of FIG. 1), and the other isheld near a surface. The fiber optic will emit a cone of light asillustrated in FIG. 4A. If the fiber optic is held perpendicular to asurface it will create a circular light pattern on the surface. As thefiber optic is raised, the radius r of the circle will increase. As thefiber optic is lowered, the radius of the light pattern will decrease.Thus, the intensity of the light (light energy per unit area) in theilluminated circular area will increase as the fiber optic is loweredand will decrease as the fiber optic is raised.

The same principle generally is true for a fiber optic being utilized asa receiver. Consider mounting a light sensor on one end of a fiber opticand holding the other end near an illuminated surface. The fiber opticcan only propagate light without loss when the light entering the fiberoptic is incident on the end of the fiber optic near the surface if thelight enters the fiber optic within its acceptance angle phi. A fiberoptic utilized as a light receiver near a surface will only accept andpropagate light from the circular area of radius r on the surface. Asthe fiber optic is raised from the surface, the area increases. As thefiber optic is lowered to the surface, the area decreases.

Consider two fiber optics parallel to each other as illustrated in FIG.4B. For simplicity of discussion, the two fiber optics illustrated areidentical in size and aperture. The following discussion, however,generally would be applicable for fiber optics that differ in size andaperture. One fiber optic is a source fiber optic, the other fiber opticis a receiver fiber optic. As the two fiber optics are heldperpendicular to a surface, the source fiber optic emits a cone of lightthat illuminates a circular area of radius r. The receiver fiber opticcan only accept light that is within its acceptance angle phi, or onlylight that is received within a cone of angle phi. If the only lightavailable is that emitted by the source fiber optic, then the only lightthat can be accepted by the receiver fiber optic is the light thatstrikes the surface at the intersection of the two circles asillustrated in FIG. 4C. As the two fiber optics are lifted from thesurface, the proportion of the intersection of the two circular areasrelative to the circular area of the source fiber optic increases. Asthey near the surface, the proportion of the intersection of the twocircular areas to the circular area of the source fiber optic decreases.If the, fiber optics are held too close to the surface (i.e., at orbelow a “critical height” h_(c)), the circular areas will no longerintersect and no light emitted from the source fiber optic will bereceived by the receiver fiber optic.

As discussed earlier, the intensity of the light in the circular areailluminated by the source fiber increases as the fiber is lowered to thesurface. The intersection of the two cones, however, decreases as thefiber optic pair is lowered. Thus, as the fiber optic pair is lowered toa surface, the total intensity of light received by the receiver fiberoptic increases to a maximal value, and then decreases sharply as thefiber optic pair is lowered still further to the surface. Eventually,the intensity will decrease essentially to zero at or below the criticalheight h_(c) (assuming the object being measured is not translucent, asdescribed more fully herein), and will remain essentially zero until thefiber optic pair is in contact with the surface. Thus, as asource-receiver pair of fiber optics as described above are positionednear a surface and as their height is varied, the intensity of lightreceived by the receiver fiber optic reaches a maximal value at a“peaking height” h_(p).

Again without being bound by theory, an interesting property of thepeaking height h_(p) has been observed. The peaking height h_(p) is afunction primarily of the geometry of fixed parameters, such as fiberapertures, fiber diameters and fiber spacing. Since the receiver fiberoptic in the illustrated arrangement is only detecting a maximum valueand not attempting to quantify the value, its maximum in general isindependent of the surface color. It is only necessary that the surfacereflect sufficient light from the intersecting area of the source andreceiver fiber optics to be within the detection range of the receiverfiber optic light sensor. Thus, in general red or green or blue or anycolor surface will all exhibit a maximum at the same peaking heighth_(p).

Although the above discussion has focused on two fiber opticsperpendicular to a surface, similar analysis is applicable for fiberoptic pairs at other angles. When a fiber optic is not perpendicular toa surface, it generally illuminates an elliptical area. Similarly, theacceptance area of a receiver fiber optic generally becomes elliptical.As the fiber optic pair is moved closer to the surface, the receiverfiber optic also will detect a maximal value at a peaking heightindependent of the surface color or characteristics. The maximalintensity value measured when the fiber optic pair is not perpendicularto the surface, however, will be less than the maximal intensity valuemeasured when the fiber optic pair is perpendicular to the surface.

Referring now to FIGS. 5A and 5B, the intensity of light received as afiber optic source-receiver pair is moved to and from a surface will nowbe described. FIG. 5A illustrates the intensity of the received light asa function of time. Corresponding FIG. 5B illustrates the height of thefiber optic pair from the surface of the object being measured. FIGS. 5Aand 5B illustrate (for ease of discussion) a relatively uniform rate ofmotion of the fiber optic pair to and from the surface of the objectbeing measured (although similar illustrations/analysis would beapplicable for non-uniform rates as well).

FIG. 5A illustrates the intensity of received light as the fiber opticpair is moved to and then from a surface. While FIG. 5A illustrates theintensity relationship for a single receiver fiber optic, similarintensity relationships would be expected to be observed for otherreceiver fiber optics, such as, for example, the multiple receiver fiberoptics of FIGS. 1 and 2. In general with the preferred embodimentdescribed above, all fifteen fiber optic receivers (of fibers 7) willexhibit curves similar to that illustrated in FIG. 5A.

FIG. 5A illustrates five regions. In region 1, the probe is movedtowards the surface of the object being measured, which causes thereceived light intensity to increase. In region 2, the probe is movedpast the peaking height, and the received light intensity peaks and thenfalls off sharply. In region 3, the probe essentially is in contact withthe surface of the object being measured. As illustrated, the receivedintensity in region 3 will vary depending upon the translucence of theobject being measured. If the object is opaque, the received lightintensity will be very low, or almost zero (perhaps out of range of thesensing circuitry). If the object is translucent, however, the lightintensity will be quite high, but in general should be less than thepeak value. In region 4, the probe is lifted and the light intensityrises sharply to a maximum value. In region 5, the probe is liftedfurther away from the object, and the light intensity decreases again.

As illustrated, two peak intensity values (discussed as P1 and P2 below)should be detected as the fiber optic pair moves to and from the objectat the peaking height h_(p). If peaks P1 and P2 produced by a receiverfiber optic are the same value, this generally is an indication that theprobe has been moved to and from the surface of the object to bemeasured in a consistent manner. If peaks P1 and P2 are of differentvalues, then these may be an indication that the probe was not moved toand from the surface of the object in a desired manner, or that thesurface is curved or textured, as described more fully herein. In such acase, the data may be considered suspect and rejected. In addition,peaks P1 and P2 for each of the perimeter fiber optics (see, e.g., FIG.2) should occur at the same peaking height (assuming the geometricattributes of the perimeter fiber optics, such as aperture, diameter andspacing from the source fiber optic, etc.). Thus, the perimeter fiberoptics of a probe moved in a consistent, perpendicular manner to andfrom the surface of the object being measured should have peaks P1 andP2 that occur at the same height. Monitoring receiver fibers from theperimeter receiver fiber optics and looking for simultaneous (or nearsimultaneous, e.g., within a predetermined range) peaks P1 and P2provides a mechanism for determining if the probe is held at a desiredperpendicular angle with respect to the object being measured.

In addition, the relative intensity level in region 3 serves as anindication of the level of translucency of the object being measured.Again, such principles generally are applicable to the totality ofreceiver fiber optics in the probe (see, e.g., fibers 7 of FIGS. 1 and3). Based on such principles, measurement techniques that may beapplicable with respect to embodiments disclosed herein will now bedescribed.

FIG. 6 is a flow chart illustrating a general measuring technique thatmay be used in accordance with certain embodiments of the presentinvention. Step 49 indicates the start or beginning of a color/opticalmeasurement. During step 49, any equipment initialization, diagnostic orsetup procedures may be performed. Audio or visual information or otherindicia may be given to the operator to inform the operator that thesystem is available and ready to take a measurement. Initiation of thecolor/optical measurement commences by the operator moving the probetowards the object to be measured, and may be accompanied by, forexample, activation of switch 17 (see FIG. 1).

In step 50, the system on a continuing basis monitors the intensitylevels for the receiver fiber optics (see, e.g., fibers 7 of FIG. 1). Ifthe intensity is rising, step 50 is repeated until a peak is detected.If a peak is detected, the process proceeds to step 52. In step 52,measured peak intensity P1, and the time at which such peak occurred,are stored in memory (such as in memory included as a part ofmicroprocessor 10), and the process proceeds to step 54. In step 54, thesystem continues to monitor the intensity levels of the receiver fiberoptics. If the intensity is falling, step 54 is repeated. If a “valley”or plateau is detected (i.e., the intensity is no longer falling, whichgenerally indicates contact or near contact with the object), then theprocess proceeds to step 56. In step 56, the measured surface intensity(IS) is stored in memory, and the process proceeds to step 58. In step58, the system continues to monitor the intensity levels of the receiverfibers. If the intensity is rising, step 58 is repeated until a peak isdetected. If a peak is detected, the process proceeds to step 60. Instep 60, measured peak intensity P2, and the time at which such peakoccurred, are stored in memory, and the process proceeds to step 62. Instep 62, the system continues to monitor the intensity levels of thereceiver fiber optics. Once the received intensity levels begin to fallfrom peak P2, the system perceives that region 5 has been entered (see,e.g., FIG. 5A), and the process proceeds to step 64.

In step 64, the system, under control of microprocessor 10, may analyzethe collected data taken by the sensing circuitry for the variousreceiver fiber optics. In step 64, peaks P1 and P2 of one or more of thevarious fiber optics may be compared. If any of peaks P1 and P2 for anyof the various receiver fiber optics have unequal peak values, then thedata may be rejected, and the entire color measuring process repeated.Again, unequal values of peaks P1 and P2 may be indicative, for example,that the probe was moved in a non-perpendicular or otherwise unstablemanner (i.e., angular or lateral movement), and, for example, peak P1may be representative of a first point on the object, while peak P2 maybe representative of a second point on the object. As the data issuspect, in a preferred embodiment of the present invention, data takenin such circumstances are rejected in step 64.

If the data are not rejected in step 64, the process proceeds to step66. In step 66, the system analyzes the data taken from theneutral-density-filtered receivers from each of the perimeter fiberoptics (e.g., R1 to R3 of FIG. 2). If the peaks of the perimeter fiberoptics did not occur at or about the same point in time, this may beindicative, for example, that the probe was not held perpendicular tothe surface of the object being measured. As non-perpendicular alignmentof the probe with the surface of the object being measured may causesuspect results, in a preferred embodiment of the present invention,data taken in such circumstances are rejected in step 66. In onepreferred embodiment, detection of simultaneous or near simultaneouspeaking (peaking within a predetermined range of time) serves as anacceptance criterion for the data, as perpendicular alignment generallyis indicated by simultaneous or near simultaneous peaking of theperimeter fiber optics. In other embodiments, step 66 includes ananalysis of peak values P1 and P2 of the perimeter fiber optics. In suchembodiments, the system seeks to determine if the peak values of theperimeter fiber optics (perhaps normalized with any initial calibrationdata) are equal within a defined range. If the peak values of theperimeter fiber optics are within the defined range, the data may beaccepted, and if not, the data may be rejected. In still otherembodiments, a combination of simultaneous peaking and equal valuedetection are used as acceptance/rejection criteria for the data, and/orthe operator may have the ability (such as through key pad switches 12)to control one or more of the acceptance criteria ranges. With suchcapability, the sensitivity of the system may be controllably altered bythe operator depending upon the particular application and operativeenvironment, etc.

If the data are not rejected in step 66, the process proceeds to step68. In step 68, the data may be processed in a desired manner to produceoutput color/optical measurement data. For example, such data may benormalized in some manner, or adjusted based on temperaturecompensation, or translucency data, or gloss data, or surface texturedata or nonperpendicular angle data or other data detected by thesystem. The data also may be converted to different display or otherformats, depending on the intended use of the data. In addition, thedata indicative of the translucence of the object and /or glossiness ofthe object also may be quantified and/or displayed in step 68. Afterstep 68, the process may proceed to starting step 49, or the process maybe terminated, etc. As indicated previously, such data also may becompared with previously-stored data for purposes of making assessmentsor predictions, etc., of a current or future condition or status.

In accordance with the process illustrated in FIG. 6, three lightintensity values (P1, P2 and IS) are stored per receiver fiber optic tomake color and translucency, etc., measurements. If stored peak valuesP1 and P2 are not equal (for some or all of the receivers), this is anindication that the probe was not held steady over one area, and thedata may be rejected (in other embodiments, the data may not berejected, although the resulting data may be used to produce an averageof the measured data). In addition, peak values P1 and P2 for the threeneutral density perimeter fiber optics should be equal or approximatelyequal; if this is not the case, then this is an indication that theprobe was not held perpendicular or a curved surface is being measured.In other embodiments, the system attempts to compensate for curvedsurfaces and/or non-perpendicular angles. In any event, if the systemcannot make a color/optical measurement, or if the data is rejectedbecause peak values P1 and P2 are unequal to an unacceptable degree orfor some other reason, then the operator is notified so that anothermeasurement or other action may be taken (such as adjust thesensitivity).

With a system constructed and operating as described above,color/optical measurements may be taken of an object, with accepted datahaving height and angular dependencies removed. Data not taken at thepeaking height, or data not taken with the probe perpendicular to thesurface of the object being measured, etc., are rejected in a certainembodiments. In other embodiments, data received from the perimeterfiber optics may be used to calculate the angle of the probe withrespect to the surface of the object being measured, and in suchembodiments non-perpendicular or curved surface data may be compensatedinstead of rejected. It also should be noted that peak values P1 and P2for the neutral density perimeter fiber optics provide a measurement ofthe luminance (gray value) of the surface of the object being measured,and also may serve to quantify the optical properties.

The translucency of the object being measured may be quantified as aratio or percentage, such as, for example, (IS/P1)×100%. In otherembodiments, other methods of quantifying translucency data provided inaccordance with the present invention are utilized, such as some otherarithmetic function utilizing IS and P1 or P2, etc. Translucenceinformation, as would be known to those in the art, could be used toquantify and/or adjust the output color data, etc.

In another particular aspect of the present invention, data generated inaccordance with the present invention may be used to implement anautomated material mixing/generation machine and/or method. Certainobjects/materials, such as dental prostheses or fillings, are made fromporcelain or other powders/resins/materials or tissue substitutes thatmay be combined in the correct ratios or modified with additives to formthe desired color of the object/prosthesis. Certain powders oftencontain pigments that generally obey Beer's law and/or act in accordancewith Kubelka-Munk equations and/or Saunderson equations (if needed) whenmixed in a recipe. Color and other data taken from a measurement inaccordance with the present invention may be used to determine orpredict desired quantities of pigment or other materials for the recipe.Porcelain powders and other materials are available in different colors,opacities, etc. Certain objects, such as dental prostheses, may belayered to simulate the degree of translucency of the desired object(such as to simulate a human tooth). Data generated in accordance withthe present invention also may be used to determine the thickness andposition of the porcelain or other material layers to more closelyproduce the desired color, translucency, surface characteristics, etc.In addition, based on fluorescence data for the desired object, thematerial recipe may be adjusted to include a desired quantity offluorescing-type material. In yet other embodiments, surfacecharacteristics (such as texture) information (as more fully describedherein) may be used to add a texturing material to the recipe, all ofwhich may be carried out in accordance with the present invention. Inyet other embodiments, the degree of surface polish to the prosthesismay be monitored or adjusted, based on gloss data derived in accordancewith the present invention.

For more information regarding such pigment-material recipe typetechnology, reference may be made to: “The Measurement of Appearance,”Second Edition, edited by Hunter and Harold, copyright 1987; “Principlesof Color Technology,” by Billmeyer and Saltzman, copyright 1981; and“Pigment Handbook,” edited by Lewis, copyright 1988. All of theforegoing are believed to have been published by John Wiley & Sons,Inc., New York, N.Y., and all of which are hereby incorporated byreference.

In certain operative environments, such as dental applications,contamination of the probe is of concern. In certain embodiments of thepresent invention, implements to reduce such contamination are provided.

FIGS. 7A and 7B illustrate a protective cap that may be used to fit overthe end of probe tip 1. Such a protective cap consists of body 80, theend of which is covered by optical window 82, which in a preferredembodiment consists of a structure having a thin sapphire window. In apreferred embodiment, body 80 consists of stainless steel. Body 80 fitsover the end of probe tip 1 and may be held into place by, for example,indentations formed in body 80, which fit with ribs 84 (which may be aspring clip or other retainer) formed on probe tip 1. In otherembodiments, other methods of affixing such a protective cap to probetip 1 are utilized. The protective cap may be removed from probe tip 1and sterilized in a typical autoclave, hot steam, chemiclave or othersterilizing system.

The thickness of the sapphire window should be less than the peakingheight of the probe in order to preserve the ability to detect peakingin accordance with the present invention, and preferably has a thicknessless than the critical height at which the source/receiver cones overlap(see FIGS. 4B and 4C). It also is believed that sapphire windows may bemanufactured in a reproducible manner, and thus any light attenuationfrom one cap to another may be reproducible. In addition, any distortionof the color/optical measurements produced by the sapphire window may becalibrated out by microprocessor 10.

Similarly, in other embodiments body 80 has a cap with a hole in thecenter (as opposed to a sapphire window), with the hole positioned overthe fiber optic source/receivers.

The cap with the hole serves to prevent the probe from coming intocontact with the surface, thereby reducing the risk of contamination. Itshould be noted that, with such embodiments, the hole is positioned sothat light from/to the light source/receiver elements of the probe tipis not adversely affected by the cap.

FIGS. 8A and 8B illustrate another embodiment of a removable probe tipthat may be used to reduce contamination in accordance with the presentinvention. As illustrated in FIG. 8A, probe tip 88 is removable, andincludes four (or a different number, depending upon the application)fiber optic connectors 90, which are positioned within optical guard 92coupled to connector 94. Optical guard 92 serves to prevent “cross talk”between adjacent fiber optics. As illustrated in FIG. 8B, in thisembodiment removable tip 88 is secured in probe tip housing 93 by way ofspring clip 96 (other removable retaining implements are utilized inother embodiments). Probe tip housing 93 may be secured to baseconnector 95 by a screw or other conventional fitting. It should benoted that, with this embodiment, different size tips may be providedfor different applications, and that an initial step of the process maybe to install the properly-sized (or fitted tip) for the particularapplication. Removable tip 88 also may be sterilized in a typicalautoclave, hot steam, chemiclave or other sterilizing system, ordisposed of. In addition, the entire probe tip assembly is constructedso that it may be readily disassembled for cleaning or repair. Incertain embodiments the light source/receiver elements of the removabletip are constructed of glass, silica or similar materials, therebymaking them particularly suitable for autoclave or similar hightemperature/pressure cleaning methods, which in certain otherembodiments the light source/receiver elements of the removable tip areconstructed of plastic or other similar materials, which may be of lowercost, thereby making them particularly suitable for disposable-typeremovable tips, etc.

In still other embodiments, a plastic, paper or other type shield (whichmay be disposable, cleanable/reusable or the like) may be used in orderto address any contamination concerns that may exist in the particularapplication. In such embodiments, the methodology may includepositioning such a shield over the probe tip prior to takingcolor/optical measurements, and may include removing anddisposing/cleaning the shield after taking color/optical measurements,etc.

A further embodiment of the present invention utilizing an alternateremovable probe tip will now be described with reference to FIGS.19A-19C. As illustrated in FIG. 19A, this embodiment utilizes removable,coherent light conduit 340 as a removable tip. Light conduit 340 is ashort segment of a light conduit that preferably may be a fused bundleof small fiber optics, in which the fibers are held essentially parallelto each other, and the ends of which are highly polished. Cross-section350 of light conduit 340 is illustrated in FIG. 19B. Light conduitssimilar to light conduit 340 have been utilized in what are known asborescopes, and also have been utilized in medical applications such asendoscopes.

Light conduit 340 in this embodiment serves to conduct light from thelight source to the surface of the object being measured, and also toreceive reflected light from the surface and conduct it to lightreceiver fiber optics 346 in probe handle 344. Light conduit 340 is heldin position with respect to fiber optics 346 by way or compression jaws342 or other suitable fitting or coupled that reliably positions lightconduit 340 so as to couple-light effectively to/from fiber optics 346.Fiber optics 346 may be separated into separate fibers/light conduits348, which may be coupled to appropriate light sensors, etc., as withpreviously described embodiments.

In general, the aperture of the fiber optics used in light conduit 340may be chosen to match the aperture of the fiber optics for the lightsource and the light receivers or alternately the light conduit aperturecould be greater than or equal to the largest source or receiveraperture. Thus, the central part of the light conduit may conduct lightfrom the light source and illuminate the surface as if it constituted asingle fiber within a bundle of fibers. Similarly, the outer portion ofthe light conduit may receive reflected light and conduct it to lightreceiver fiber optics as if it constituted single fibers. Light conduit340 has ends that preferably are highly polished and cut perpendicular,particularly the end coupling light to fiber optics 346. Similarly, theend of fiber optics 346 abutting light conduit 340 also is highlypolished and cut perpendicular to a high degree of accuracy in order tominimize light reflection and cross talk between the light source fiberoptic and the light receiver fiber optics and between adjacent receiverfiber optics. Light conduit 340 offers significant advantages includingin the manufacture and installation of such a removable tip. Forexample, the probe tip need not be particularly aligned with the probetip holder; rather, it only needs to be held against the probe tipholder such as with a compression mechanism (such as with compressionjaws 342) so as to couple light effectively to/from fiber optics 346.Thus, such a removable tip mechanism may be implemented withoutalignment tabs or the like, thereby facilitating easy installation ofthe removable probe tip. Such an easy installable probe tip may thus beremoved and cleaned prior to installation, thereby facilitating use ofthe color/optical measuring apparatus by dentists, medical professionsor others working in an environment in which contamination may be aconcern. Light conduit 340 also may be implemented, for example, as asmall section of light conduit, which may facilitate easy and low costmass production and the like.

A further embodiment of such a light conduit probe tip is illustrated aslight conduit 352 in FIG. 19C. Light conduit 352 is a light conduit thatis narrower on one end (end 354) than the other end (end 356).Contoured/tapered light conduits such as light conduit 352 may befabricated by heating and stretching a bundle of small fiber optics aspart of the fusing process. Such light conduits have an additionalinteresting property of magnification or reduction. Such phenomenaresult because there are the same number of fibers in both ends. Thus,light entering narrow end 354 is conducted to wider end 356, and sincewider end 356 covers a larger area, it has a magnifying affect.

Light conduit 352 of FIG. 19C may be utilized in a manner similar tolight conduit 340 (which in general may be cylindrical) of FIG. 19A.Light conduit 352, however, measures smaller areas because of itsreduced size at end 354. Thus, a relatively larger probe body may bemanufactured where the source fiber optic is spaced widely from thereceiver fiber optics, which may provide an advantage in reduced lightreflection and cross talk at the junction, while still maintaining asmall probe measuring area. Additionally, the relative sizes of narrowend 354 of light conduit 352 may be varied. This enables the operator toselect the size/characteristic of the removable probe tip according tothe conditions in the particular application. Such ability to selectsizes of probe tips provides a further advantage in making opticalcharacteristics measurements in a variety of applications and operativeenvironments.

As should be apparent to those skilled in the art in view of thedisclosures herein, light conduits 340 and 356 of FIGS. 19A and 19C neednot necessarily be cylindrical/tapered as illustrated, but may be curvedsuch as for specialty applications, in which a curved probe tip may beadvantageously employed (such as in a confined or hard-to-reach place).It also should be apparent that light conduit 352 of FIG. 19C may bereversed (with narrow end 354 coupling light into fiber optics 346,etc., and wide end 356 positioned in order to take measurements) inorder to cover larger areas.

With reference to FIG. 9, a tristimulus embodiment will now bedescribed, which may aid in the understanding of, or may be used inconjunction with, certain embodiments disclosed herein. In general, theoverall system depicted in FIG. 1 and discussed in detail elsewhereherein may be used with this embodiment. FIG. 9 illustrates a crosssection of the probe tip fiber optics used in this embodiment.

Probe tip 100 includes central source fiber optic 106, surrounded by(and spaced apart from) three perimeter receiver fiber optics 104 andthree color receiver fiber optics 102. Three perimeter receiver fiberoptics 104 are optically coupled to neutral density filters and serve asheight/angle sensors in a manner analogous to the embodiment describeabove. Three color receiver fiber optics are optically coupled tosuitable tristimulus filters, such as red, green and blue filters. Withthis embodiment, a measurement may be made of tristimulus color valuesof the object, and the process described with reference to FIG. 6generally is applicable to this embodiment. In particular, perimeterfiber optics 104 may be used to detect simultaneous peaking or otherwisewhether the probe is perpendicular to the object being measured.

FIG. 10A illustrates another such embodiment, similar to the embodimentdiscussed with reference to FIG. 9. Probe tip 100 includes centralsource fiber optic 106, surrounded by (and spaced apart from) threeperimeter receiver fiber optics 104 and a plurality of color receiverfiber optics 102. The number of color receiver fiber optics 102, and thefilters associated with such receiver fiber optics 102, may be chosenbased upon the particular application. As with the embodiment of FIG. 9,the process described with reference to FIG. 6 generally is applicableto this embodiment.

FIG. 10B illustrates another such embodiment in which there are aplurality of receiver fiber optics that surround central source fiberoptic 240. The receiver fiber optics are arranged in rings surroundingthe central source fiber optic. FIG. 10B illustrates three rings ofreceiver fiber optics (consisting of fiber optics 242, 244 and 246,respectively), in which there are six receiver fiber optics per ring.The rings may be arranged in successive larger circles as illustrated tocover the entire area of the end of the probe, with the distance fromeach receiver fiber optic within a given ring to the central fiber opticbeing equal (or approximately so). Central fiber optic 240 is utilizedas the light source fiber optic and is connected to the light source ina manner similar to light source fiber optic 5 illustrated in FIG. 1.

The plurality of receiver fiber optics are each coupled to two or morefiber optics in a manner similar to the arrangement illustrated in FIG.1 for splicing connector 4. One fiber optic from such a splicingconnector for each receiver fiber optic passes through a neutral densityfilter and then to light sensor circuitry similar to the light sensorcircuitry illustrated in FIG. 3. A second fiber optic from the splicingconnector per receiver fiber optic passes through a Sharp CuttingWrattan Gelatin Filter (or notch filter as previously described) andthen to light sensor circuitry as discussed elsewhere herein. Thus, eachof the receiver fiber optics in the probe tip includes both colormeasuring elements and neutral light measuring or “perimeter” elements.

FIG. 10D illustrates the geometry of probe 260 (such as described above)illuminating an area on flat diffuse surface 272. Probe 260 createslight pattern 262 that is reflected diffusely from surface 272 inuniform hemispherical pattern 270. With such a reflection pattern, thereflected light that is incident upon the receiving elements in theprobe will be equal (or nearly equal) for all elements if the probe isperpendicular to the surface as described above herein.

FIG. 10C illustrates a probe illuminating rough surface 268 or a surfacethat reflects light unevenly. The reflected light will exhibit hot spotsor regions 266 where the reflected light intensity is considerablygreater than it is on other areas 264. The reflected light pattern willbe uneven when compared to a smooth surface as illustrate in FIG. 10D.

Since a probe as illustrated in FIG. 10B has a plurality of receiverfiber optics arranged over a large surface area, the probe may beutilized to determine the surface texture of the surface as well asbeing able to measure the color and translucency, etc., of the surfaceas described earlier herein. If the light intensity received by thereceiver fiber optics is equal for all fiber optics within a given ringof receiver fiber optics, then generally the surface is smooth. If,however, the light intensity of receiver fibers in a ring varies withrespect to each other, then generally the surface is rough. By comparingthe light intensities measured within receiver fiber optics in a givenring and from ring to ring, the texture and other characteristics of thesurface may be quantified.

FIG. 11 illustrates an embodiment of the present invention in whichlinear optical sensors and a color gradient filter are utilized insteadof light sensors 8 (and filters 22, etc.). Receiver fiber optics 7,which may be optically coupled to probe tip 1 as with the embodiment ofFIG. 1, are optically coupled to linear optical sensor 112 through colorgradient filter 110. In this embodiment, color gradient filter 110 mayconsist of series of narrow strips of cut-off type filters on atransparent or open substrate, which are constructed so as topositionally correspond to the sensor areas of linear optical sensor112. An example of a commercially available linear optical sensor 112 isTexas Instruments part number TSL213, which has 61 photo diodes in alinear array. Light receiver fiber optics 7 are arranged correspondinglyin a line over linear optical sensor 112. The number of receiver fiberoptics may be chosen for the particular application, so long as enoughare included to more or less evenly cover the full length of colorgradient filter 110. With this embodiment, the light is received andoutput from receiver fiber optics 7, and the light received by linearoptical sensor 112 is integrated for a short period of time (determinedby the light intensity, filter characteristics and desired accuracy).The output of linear array sensor 112 is digitized by ADC 114 and outputto microprocessor 116 (which may the same processor as microprocessor 10or another processor)

In general, with the embodiment of FIG. 11, perimeter receiver fiberoptics may be used as with the embodiment of FIG. 1, and in general theprocess described with reference to FIG. 6 is applicable to thisembodiment.

FIG. 12 illustrates an embodiment of the present invention in which amatrix optical sensor and a color filter grid are utilized instead oflight sensors 8 (and filters 22, etc.). Receiver fiber optics 7, whichmay be optically coupled to probe tip 1 as with the embodiment of FIG.1, are optically coupled to matrix optical sensor 122 through filtergrid 120. Filter grid 120 is a filter array consisting of a number ofsmall colored spot filters that pass narrow bands of visible light.Light from receiver fiber optics 7 pass through corresponding filterspots to corresponding points on matrix optical sensor 122. In thisembodiment, matrix optical sensor 122 may be a monochrome optical sensorarray, such as CCD-type or other type of light sensor element such asmay be used in a video camera. The output of matrix optical sensor 122is digitized by ADC 124 and output to microprocessor 126 (which may thesame processor as microprocessor 10 or another processor). Under controlof microprocessor 126, matrix optical sensor 126 collects data fromreceiver fiber optics 7 through color filter grid 120.

In general, with the embodiment of FIG. 12, perimeter receiver fiberoptics may be used as with the embodiment of FIG. 1, and in general theprocess described with reference to FIG. 6 also is applicable to thisembodiment.

In general with the embodiments of FIGS. 11 and 12, the color filtergrid may consist of sharp cut off filters as described earlier or it mayconsist of notch filters. As will be apparent to one skilled in the art,they may also be constructed of a diffraction grating and focusingmirrors such as those utilized in conventional monochromators.

As will be clear from the foregoing description, with the presentinvention a variety of types of spectral color/optical photometers (ortristimulus-type colorimeters) may be constructed, with perimeterreceiver fiber optics used to collect color/optical data essentiallyfree from height and angular deviations. In addition, in certainembodiments, the present Invention enables color/optical measurements tobe taken at a peaking height from the surface of the object beingmeasured, and thus color/optical data may be taken without physicalcontact with the object being measured (in such embodiments, thecolor/optical data is taken only by passing the probe through region 1and into region 2, but without necessarily going into region 3 of FIGS.5A and 5B). Such embodiments may be utilized if contact with the surfaceis undesirable in a particular application. In the embodiments describedearlier, however, physical contact (or near physical contact) of theprobe with the object may allow all five regions of FIGS. 5A and 5B tobe utilized, thereby enabling measurements to be taken such thattranslucency information also may be obtained. Both types of embodimentsgenerally are within the scope of the invention described herein.

Additional description will now be provided with respect to cut-offfilters of the type described in connection with the preferredembodiment(s) of FIGS. 1 and 3 (such as filters 22 of FIG. 3). FIG. 13Aillustrates the properties of a single Kodak Sharp Cutting WrattenGelatin Filter discussed in connection with FIG. 3. Such a cut-offfilter passes light below a cut-off frequency (i.e., above a cut-offwavelength). Such filters may be manufactured to have a wide range ofcut-off frequencies/wavelengths. FIG. 13B illustrates a number of suchfilters, twelve in a preferred embodiment, with cut-offfrequencies/wavelengths chosen so that essentially the entire visibleband is covered by the collection of cut-off filters.

FIGS. 14A and 14B illustrate exemplary intensity measurements using acut-off filter arrangement such as illustrated in FIG. 13B, first in thecase of a white surface being measured (FIG. 14A), and also in the caseof a blue surface being measured (FIG. 14B). As illustrated in FIG. 14A,in the case of a white surface, the neutrally filtered perimeter fiberoptics, which are used to detect height and angle, etc., generally willproduce the highest intensity (although this depends at least in partupon the characteristics of the neutral density filters). As a result ofthe stepped cut-off filtering provided by filters having thecharacteristics illustrated in FIG. 13B, the remaining intensities willgradually decrease in value as illustrated in FIG. 14A. In the case of ablue surface, the intensities will decrease in value generally asillustrated in FIG. 14B. Regardless of the surface, however, theintensities out of the filters will always decrease in value asillustrated,-with the greatest intensity value being the output of thefilter having the lowest wavelength cut-off value (i.e., passes allvisible light up to blue), and the lowest intensity value being theoutput of the filter having the highest wavelength cut-off (i.e., passesonly red visible light). As will be understood from the foregoingdescription, any color data detected that does not fit the decreasingintensity profiles of FIGS. 14A and 14B may be detected as anabnormality, and in certain embodiments detection of such a conditionresults in data rejection, generation of an error message or initiationof a diagnostic routine, etc.

Reference should be made to the FIGS. 1 and 3 and the relateddescription for a detailed discussion of how such a cut-off filterarrangement may be utilized in accordance with the present invention.

FIG. 15 is a flow chart illustrating audio tones that may be used incertain preferred embodiments of the present invention. It has beendiscovered that audio tones (such as tones, beeps, voice or the likesuch as will be described) present a particularly useful and instructivemeans to guide an operator in the proper use of a color measuring systemof the type described herein.

The operator may initiate a color/optical measurement by activation of aswitch (such as switch 17 of FIG. 1) at step 150. Thereafter, if thesystem is ready (set-up, initialized, calibrated, etc.), alower-the-probe tone is emitted (such as through speaker 16 of FIG. 1)at step 152. The system attempts to detect peak intensity P1 at step154. If a peak is detected, at step 156 a determination is made whetherthe measured peak P1 meets the applicable criteria (such as discussedabove in connection with FIGS. 5A, 5B and 6). If the measured peak P1 isaccepted, a first peak acceptance tone is generated at step 160. If themeasured peak P1 is not accepted, an unsuccessful tone is generated atstep 158, and the system may await the operator to initiate a furthercolor/optical measurement. Assuming that the first peak was accepted,the system attempts to detect peak intensity P2 at step 162. If a secondpeak is detected, at step 164 a determination is made whether themeasured peak P2 meets the applicable criteria. If the measured peak P2is accepted the process proceeds to color calculation step 166 (in otherembodiments, a second peak acceptance tone also is generated at step166). If the measured peak P2 is not accepted, an unsuccessful tone isgenerated at step 158, and the system may await the operator to initiatea further color/optical measurement. Assuming that the second peak wasaccepted, a color/optical calculation is made at step 166 (such as, forexample, microprocessor 10 of FIG. 1 processing the data output fromlight sensors 8, etc.). At step 168, a determination is made whether thecolor calculation meets the applicable criteria. If the colorcalculation is accepted, a successful tone is generated at step 170. Ifthe color calculation is not accepted, an unsuccessful tone is generatedat step 158, and the system may await the operator to initiate a furthercolor/optical measurement.

With unique audio tones presented to an operator in accordance with theparticular operating state of the system, the operator's use of thesystem may be greatly facilitated. Such audio information also tends toincrease operator satisfaction and skill level, as, for example,acceptance tones provide positive and encouraging feedback when thesystem is operated in a desired manner.

Further embodiments of the present invention will now be described withreference to FIGS. 16-18. The previously described embodiments generallyrely on movement of the probe with respect to the object being measured.While such embodiments provide great utility in many applications, incertain applications, such as robotics, industrial control, automatedmanufacturing, etc. (such as positioning the object and/or the probe tobe in proximity to each other, detecting color/optical properties of theobject, and then directing the object, e.g., sorting, based on thedetected color/optical properties, for further industrial processing,packaging, etc.) it may be desired to have the measurement made with theprobe held or positioned substantially stationary above the surface ofthe object to be measured (in such embodiments, the positioned probe maynot be handheld as with certain other embodiments).

FIG. 16 illustrates such a further embodiment. The probe of thisembodiment includes a plurality of perimeter sensors and a plurality ofcolor sensors coupled to receivers 312-320. The color sensors andrelated components, etc., may be constructed to operate in a manneranalogous to previously described embodiments. For example, fiber opticcables or the like may couple light from source 310 that is received byreceivers 312-320 to sharp cut-off filters or notch filters, with thereceived light measured over precisely defined wavelengths (see, e.g.,FIGS. 1, 3 and 11-14 and related description). Color/opticalcharacteristics of the object may be determined from the plurality ofcolor sensor measurements, which may include three such sensors in thecase of a tristimulus instrument, or 8, 12, 15 or more color sensors fora more full bandwidth system (the precise number may be determined bythe desired color resolution, etc.).

With this embodiment, a relatively greater number of perimeter sensorsare utilized (as opposed, for example, to the three perimeter sensorsused in certain preferred embodiments of the present invention). Asillustrated in FIG. 16, a plurality of triads of receivers 312-320coupled to perimeter sensors are utilized, where each triad in thepreferred implementation consists of three fiber optics positioned equaldistance from light source 310, which in the preferred embodiment is acentral light source fiber optic. The triads of perimeterreceivers/sensors may be configured as concentric rings of sensorsaround the central light source fiber optic. In FIG. 16, ten such triadrings are illustrated, although in other embodiments a lesser or greaternumber of triad rings may be utilized, depending upon the desiredaccuracy and range of operation, as well as cost considerations and thelike.

The probe illustrated in FIG. 16 may operate within a range of heights(i.e., distances from the object being measured). As with earlierembodiments, such height characteristics are determined primarily by thegeometry and constituent materials of the probe, with the spacing of theminimal ring of perimeter sensors determining the minimal height, andthe spacing of the maximal ring of perimeter sensors determining themaximum height, etc. It therefore is possible to construct probes ofvarious height ranges and accuracy, etc., by varying the number ofperimeter sensor rings and the range of ring distances from the centralsource fiber optic. It should be noted that such embodiments may beparticularly suitable when measuring similar types of materials, etc.

As described earlier, the light receiver elements for the plurality ofreceivers/perimeter sensors may be individual elements such as TexasInstruments TSL230 light-to-frequency converters, or may be constructedwith rectangular array elements or the like such as may be found in aCCD camera. Other broadband-type of light measuring elements areutilized in other embodiments. Given the large number of perimetersensors used in such embodiments (such as 30 for the embodiment of FIG.16), an array such as CCD camera-type sensing elements may be desirable.It should be noted that the absolute intensity levels of light measuredby the perimeter sensors is not as critical to such embodiments of thepresent invention; in such embodiments differences between the triads ofperimeter light sensors are advantageously utilized in order to obtainoptical measurements.

Optical measurements may he made with such a probe byholding/positioning the probe near the surface of the object beingmeasured (i.e., within the range of acceptable heights of the particularprobe). The light source providing light to light source 310 is turnedon and the reflected light received by receivers 312-320 (coupled to theperimeter sensors) is measured. The light intensity of the rings oftriad sensors is compared. Generally, if the probe is perpendicular tothe surface and if the surface is flat, the light intensity of the threesensors of each triad should be approximately equal. If the probe is notperpendicular to the surface or if the surface is not flat, the lightintensity of the three sensors within a triad will not be equal. It isthus possible to determine if the probe is perpendicular to the surfacebeing measured, etc. It also is possible to compensate fornon-perpendicular surfaces by mathematically adjusting the lightintensity measurements of the color sensors with the variance inmeasurements of the triads of perimeters sensors.

Since the three sensors forming triads of sensors are at differentdistances (radii) from central light source 310, it is expected that thelight intensities measured by light receivers 312-320 and the perimetersensors will vary. For any given triad of sensors, as the probe is movedcloser to the surface, the received light intensity will increase to amaximum and then sharply decrease as the probe is moved closer to thesurface. As with previously-described embodiments, the intensitydecreases rapidly as the probe is moved less than the peaking height anddecreases rapidly to zero or almost zero for opaque objects. The valueof the peaking height depends principally upon the distance of theparticular receiver from light source 310. Thus, the triads of sensorswill peak at different peaking heights. By analyzing the variation inlight values received by the triads of sensors, the height of the probecan be determined. Again, this is particularly true when measuringsimilar types of materials. As discussed earlier, comparisons withpreviously-stored data also may be utilized to make such determinationsor assessments, etc.

The system initially is calibrated against a neutral background (e.g., agray background), and the calibration values are stored in non-volatilememory (see, e.g., processor 10 of FIG. 1). For any given color orintensity, the intensity for the receivers/perimeter sensors(independent of distance from the central source fiber optic) in generalshould vary equally. Hence, a white surface should produce the highestintensities for the perimeter sensors, and a black surface will producethe lowest intensities. Although the color of the surface will affectthe measured light intensities of the perimeter sensors, it shouldaffect them substantially equally. The height of the probe from thesurface of the object, however, will affect the triads of sensorsdifferently. At the minimal height range of the probe, the triad ofsensors in the smallest ring (those closest to the source fiber optic)will be at or about their maximal value. The rest of the rings of triadswill be measuring light at intensities lower than their maximal values.As the probe is raised/positioned from the minimal height, the intensityof the smallest ring of sensors will decrease and the intensity of thenext ring of sensors will increase to a maximal value and will thendecrease in intensity as the probe is raised/positioned still further.Similarly for the third ring, fourth ring and so on. Thus, the patternof intensities measured by the rings of triads will be height dependent.In such embodiments, characteristics of this pattern may be measured andstored in non-volatile RAM look-up tables (or the like) for the probe bycalibrating it in a fixture using a neutral color surface. Again, theactual intensity of light is not as important in such embodiments, butthe degree of variance from one ring of perimeter sensors to another is.

To determine a measure of the height of the probe from the surface beingmeasured, the intensities of the perimeter sensors (coupled to receivers312-320) is measured. The variance in light intensity from the innerring of perimeter sensors to the next ring and so on is analyzed andcompared to the values in the look-up table to determine the height ofthe probe. The determined height of the probe with respect to thesurface thus may be utilized by the system processor to compensate forthe light intensities measured by the color sensors in order to obtainreflectivity readings that are in general independent of height. As withpreviously described embodiments, the reflectivity measurements may thenbe used to determine optical characteristics of the object beingmeasured, etc.

It should be noted that audio tones, such as previously described, maybe advantageously employed when such an embodiment is used in a handheldconfiguration. For example, audio tones of varying pulses, frequenciesand/or intensities may be employed to indicate the operational status ofthe instrument, when the instrument is positioned within an acceptablerange for color measurements, when valid or invalid color measurementshave been taken, etc. In general, audio tones as previously describedmay be adapted for advantageous use with such further embodiments.

FIG. 17 illustrates a further such embodiment of the present invention.The preferred implementation of this embodiment consists of a centrallight source 310 (which in the preferred implementation is a centrallight source fiber optic), surrounded by a plurality of light receivers322 (which in the preferred implementation consists of three perimeterlight receiver fiber optics). The three perimeter light receiver fiberoptics, as with earlier described embodiments, may be each spliced intoadditional fiber optics that pass to light intensity receivers/sensors,which may be implemented with Texas Instruments TSL230 light tofrequency converters as described previously. One fiber of eachperimeter receiver is coupled to a sensor and measured full band width(or over substantially the same bandwidth) such as via a neutral densityfilter, and other of the fibers of the perimeter receivers are coupledto sensors so that the light passes through sharp cut off or notchfilters to measure the light intensity over distinct frequency ranges oflight (again, as with earlier described embodiments). Thus there arecolor light sensors and neutral “perimeter” sensors as with previouslydescribed embodiments. The color sensors are utilized to determine thecolor or other optical characteristics of the object, and the perimetersensors are utilized to determine if the probe is perpendicular to thesurface and/or are utilized to compensate for non-perpendicular angleswithin certain angular ranges.

In the embodiment of FIG. 17, the angle of the perimeter sensor fiberoptics is mechanically varied with respect to the central source fiberoptic. The angle of the perimeter receivers/sensors with respect to thecentral source fiber optic is measured and utilized as describedhereinafter. An exemplary mechanical mechanism, the details of which arenot critical so long as desired, control movement of the perimeterreceivers with respect to the light source is obtained, is describedwith reference to FIG. 18.

The probe is held within the useful range of the instrument (determinedby the particular configuration and construction, etc.), and a colormeasurement is initiated. The angle of the perimeter receivers/sensorswith respect to the central light source is varied from parallel topointing towards the central source fiber optic. While the angle isbeing varied, the intensities of the light sensors for the perimetersensors (e.g., neutral sensors) and the color sensors is measured andsaved along with the angle of the sensors at the time of the lightmeasurement. The light intensities are measured over a range of angles.As the angle is increased the light intensity will increase to a maximumvalue and will then decrease as the angle is further increased. Theangle where the light values is a maximum is utilized to determine theheight of the probe from the surface. As will be apparent to thoseskilled in the art based on the teachings provided herein, with suitablecalibration data, simple geometry or other math, etc., may be utilizedto calculate the height based on the data measured during variation ofthe angle. The height measurement may then be utilized to compensate forthe intensity of the color/optical measurements and/or utilized tonormalize color values, etc.

FIG. 18 illustrates an exemplary embodiment of a mechanical arrangementto adjust and measure the angle of the perimeter sensors. Each perimeterreceiver/sensor 329 IS mounted with pivot arm 326 on probe frame 328.Pivot arm 326 engages central ring 332 in a manner to form a cammechanism. Central ring 332 includes a groove that holds a portion ofpivot arm 326 to form the cam mechanism. Central ring 332 may be movedperpendicular with respect to probe frame 328 via linear actuator 324and threaded spindle 330. The position of central ring 332 with respectto linear actuator 324 determines the angle of perimeterreceivers/sensors 322 with respect to light source 310. Such angularposition data vis-a-vis the position of linear actuator 324 may becalibrated in advance and stored in non-volatile memory, and later usedto produce color/optical characteristic measurement data as previouslydescribed.

With the foregoing as background, various additional preferredembodiments utilizing variable aperture receivers in order to measure,for example, the degree of gloss of the surface will now be describedwith references to FIGS. 20A to 22B. Various of the electronics andspectrophotometer/reflectometer implements described above will beapplicable to such preferred embodiments.

Referring to FIG. 20A, a probe utilizing variable aperture receiverswill now be described. In FIG. 20A, source A 452 represents a sourcefiber optic of a small numerical aperture NA, 0.25 for example;receivers B 454 represent receiver fiber optics of a wider numericalaperture, 0.5 for example; receivers C 456 represent receiver fiberoptics of the same numerical aperture as source A but is shown with asmaller core diameter; and receivers D 458 represent receiver fiberoptics of a wider numerical aperture, 0.5 for example.

One or more of receiver(s) B 454 (in certain embodiments one receiver Bmay be utilized, while in other embodiments a plurality of receivers Bare utilized, which may be circularly arranged around source A, such as6 or 8 such receivers B) pass to a spectrometer (see, e.g., FIGS. 1, 3,11, 12, configured as appropriate for such preferred embodiments).Receiver(s) B 454 are used to measure the spectrum of the reflectedlight. Receivers C 456 and D 458 pass to broad band (wavelength) opticalreceivers and are used to correct the measurement made by receiver(s) B.Receivers C 456 and D 458 are used to correct for and to detect whetheror not the probe is perpendicular to the surface and to measure/assessthe degree of specular versus diffuse reflection (the coefficient ofspecular reflection, etc.) and to measure the translucency of thematerial/object.

FIG. 20B illustrates a refinement of the embodiment of FIG. 20A, inwhich receivers B 454 are replaced by a cylindrical arrangement ofclosely packed, fine optical fibers 454A, which generally surround lightsource 452 as illustrated. The fibers forming the cylindricalarrangement for receivers B 454A, are divided into smaller groups offibers and are presented, for example, to light sensors 8 shown in FIG.1. The number of groups of fibers is determined by the number of lightsensors. Alternately, the entire bundle of receiver fibers B 454A ispresented to a spectrometer such as a diffraction grating spectrometerof conventional design. As previously described, receivers C 456 and D458 may be arranged on the periphery thereof. In certain embodiments,receivers C and D may also consist of bundles of closely packed, fineoptical fibers. In other embodiments they consist of single fiberoptics.

The assessment of translucency in accordance with embodiments of thepresent invention have already been described. It should be noted,however, that in accordance with the preferred embodiment both the lightreflected from the surface of the material/object (i.e., the peakingintensity) and its associated spectrum and the spectrum of the lightwhen it is in contact with the surface of the material/object may bemeasured/assessed. The two spectrums typically will differ in amplitude(the intensity or luminance typically will be greater above the surfacethan in contact with the surface) and the spectrums for certainmaterials may differ in chrominance (i.e., the structure of thespectrum) as well.

When a probe in accordance with such embodiments measures the peakingintensity, it in general is measuring both the light reflected from thesurface and light that penetrates the surface, gets bulk scatteredwithin the material and re-emerges from the material (e.g., the resultof translucency). When the probe is in contact with the surface (e.g.,less than the critical height), no light reflecting from the surface canbe detected by the receiver fiber optics, and thus any light detected bythe receivers is a result of the translucency of the material and itsspectrum is the result of scattering within the bulk of the material.The “reflected spectrum” and the “bulk spectrum” in general may bedifferent for different materials, and assessments of such reflected andbulk spectrum provide additional parameters for measuring, assessingand/or characterizing materials, surfaces, objects, teeth, etc., andprovide new mechanisms to distinguish translucent and other types ofmaterials.

In accordance with preferred embodiments of the present invention, anassessment or measurement of the degree of gloss (or specularreflection) may be made. For understanding thereof, reference is made toFIGS. 21 to 22B.

Referring to FIG. 21, consider two fiber optics, source fiber optic 460and receiver fiber optic 462, arranged perpendicular to a specularsurface as illustrated. The light reflecting from a purely specularsurface will be reflected in the form of a cone. As long as thenumerical aperture of the receiver fiber optic is greater than or equalto the numerical aperture of the source fiber optic, all the lightreflected from the surface that strikes the receiver fiber optic will bewithin the receiver fiber optic's acceptance cone and will be detected.In general, it does not matter what the numerical aperture of thereceiver fiber optic is, so long as it is greater than or equal to thenumerical aperture of the source fiber optic. When the fiber optic pairis far from the surface, receiver fiber optic 462 is fully illuminated.Eventually, as the pair approaches surface 464, receiver fiber optic 462is only partially illuminated. Eventually, at heights less than or equalto the critical height h_(c) receiver fiber optic 462 will not beilluminated. In general, such as for purely specular surfaces, it shouldbe noted that the critical height is a function of the numericalaperture of source fiber optic 460, and is not a function of thenumerical aperture of the receiver.

Referring now to FIGS. 22A and 22B, consider two fiber optics (source460 and receiver 462) perpendicular to diffuse surface 464A asillustrated in FIG. 22A (FIG. 22B depicts mixed specular/diffuse surface464B and area of intersection 466B). Source fiber optic 460 illuminatescircular area 466A on surface 464A, and the light is reflected fromsurface 464A. The light, however, will be reflected at all angles,unlike a specular surface where the light will only be reflected in theform of a cone. Receiver fiber optic 462 in general is alwaysilluminated at all heights, although it can only propagate and detectlight that strikes its surface at an angle less than or equal to itsacceptance angle. Thus, when the fiber optic pair is less than thecritical height, receiver fiber optic 462 detects no light. As theheight increases above the critical height, receiver fiber optic 462starts to detect light that originates from the area of intersection ofthe source and receiver cones as illustrated. Although light may, beincident upon receiver fiber optic 462 from other areas of theilluminated circle, it is not detected because it is greater than theacceptance angle of the receiver fiber.

As the numerical aperture of receiver fiber optic 462 increases, theintensity detected by receiver fiber optic 462 will increase for diffusesurfaces, unlike a specular surface where the received intensity is nota function of receiver fiber optic numerical aperture. Thus, for a probeconstructed with a plurality of receiver fiber optics with differentnumerical apertures, as in preferred embodiments of the presentinvention, if the surface is a highly glossy surface, both receivers(see, e.g., receivers 456 and 458 of FIG. 20A, will measure the samelight intensity. As the surface becomes increasingly diffuse, howeverreceiver D 458 will have a greater intensity than receiver C 456. Theratio of the two intensities from receivers C/D is a measure of, orcorrelates to, the degree of specular reflection of the material, andmay be directly or indirectly used to quantify the “glossiness” of thesurface. Additionally, it should be noted that generally receiver C 456(preferably having the same numerical aperture as source fiber optic A452) measures principally the specular reflected component. Receiver D458, on the other hand, generally measures both diffuse and specularcomponents. As will be appreciated by those skilled in the art, suchprobes and methods utilizing receivers of different/varying numericalapertures may be advantageously utilized, with or without additionaloptical characteristic determinations as described elsewhere herein, tofurther quantify materials such as teeth or other objects.

Referring now to FIG. 23A, additional preferred embodiments will bedescribed. The embodiment of FIG. 23A utilizes very narrow numericalaperture, non-parallel fiber optic receivers 472 and very narrownumerical aperture source fiber optic 470 or utilizes other opticalelements to create collimated or nearly collimated source and receiverelements. Central source fiber optic 470 is a narrow numerical aperturefiber optic and receiver fiber optics 472 as illustrated (preferablymore than two such receivers are utilized in such embodiments) are alsonarrow fiber optics. Other receiver fiber optics may be wide numericalaperture fiber optics (e.g., receivers such as receivers 458 of FIG.20A). As illustrated, receiver fiber optics 472 of such embodiments areat an angle with respect to source fiber optic 470, with the numericalaperture of the receiver fiber optics selected such that, when thereceived intensity peaks as the probe is lowered to the surface, thereceiver fiber optics' acceptance cones intersect with the entirecircular area illuminated by the source fiber optic, or at least with asubstantial portion of the area illuminated by the source. Thus, thereceivers generally are measuring the same central spot illuminated bythe source fiber optic.

A particular aspect of such embodiments is that a specular excludedprobe/measurement technique may be provided. In general, the spectrallyreflected light is not incident upon the receiver fiber optics, and thusthe probe is only sensitive to diffuse light. Such embodiments may beuseful for coupling reflected light to a multi-band spectrometer (suchas described previously) or to more wide band sensors. Additionally,such embodiments may be useful as a part of a probe/measurementtechnique utilizing both specular included and specular excludedsensors. An illustrative arrangement utilizing such an arrangement isshown in FIG. 23B. In FIG. 23B, element 470 may consist of a sourcefiber optic, or alternatively may consist of all or part of the elementsshown in cross-section in FIG. 20A or 20B. Still alternatively,non-parallel receiver fiber optics 472 may be parallel along theirlength but have a machined, polished, or other finished or other bentsurface on the end thereof in order to exclude all, or a substantial orsignificant portion, of the specularly reflected light. In otherembodiments, receiver fiber optics 472 may contain optical elementswhich exclude specularly reflected light. An additional aspect ofembodiments of the present invention is that they may be more fullyintegrated with a camera. Referring now to FIGS. 24 to 26, various ofsuch embodiments will be described for illustrative purposes. In suchembodiments, optical characteristic measurement implements such aspreviously described may be more closely integrated with a camera,including common chassis 480, common cord or cable 482, and common probe484. In one such alternative preferred embodiment, camera optics 486 arepositioned adjacent to spectrometer optics 488 near the end of probe484, such as illustrated in FIG. 25. Spectrometer optics 488 mayincorporate, for example, elements of color and other opticalcharacteristics measuring embodiments described elsewhere herein, suchas shown in FIGS. 1-3, 9-10B, 11-12, 16-17, 20A, 20B and 23A and 23B. Inanother embodiment, camera optics and lamp/light source 490 ispositioned near the end of probe 484, around which are positioned aplurality of light receivers 492. Camera optics and lamp/light source490 provide illumination and optics for the camera sensing element and alight source for making color/optical characteristics in accordance withtechniques described elsewhere herein. It should be noted that lightreceivers 492 are shown as a single ring for illustrative purposes,although in other embodiments light receivers such as describedelsewhere herein (such as in the above-listed embodiments includingmultiple rings/groups, etc.) may be utilized in an analogous manner.Principles of such camera optics generally are known in the borescope orendoscopes fields.

With respect to such embodiments, one instrument may be utilized forboth camera uses and for quantifying the optical properties of teeth.The camera may be utilized for showing patients the general state of thetooth, teeth or other dental health, or for measuring certain propertiesof teeth or dental structure such as size and esthetics or for colorpostureization as previously described. The optical characteristicmeasuring implement may then measure the optical properties of the teethsuch as previously described herein. In certain embodiments, such asillustrated in FIGS. 25 and 26, a protective shield is placed over thecamera for use in a conventional manner, and the protective shield isremoved and a specialized tip is inserted into spectrometer optics 488or over camera optics and lamp/light source 490 and light receivers 492(such tips may be as discussed in connection with FIGS. 23A-23C, with asuitable securing mechanism) for infection control, thereby facilitatingmeasuring and quantifying the optical properties. In other embodiments acommon protective shield (preferably thin and tightly fitted, andoptically transparent, such as are known for cameras) that covers boththe camera portion and spectrometer portion are utilized.

Based on the foregoing embodiments, with which translucency and glossmay be measured or assessed, further aspects of the present inventionwill be described. As previously discussed, when light strikes anobject, it may be reflected from the surface, absorbed by the bulk ofthe material, or it may penetrate into the material and either beemitted from the surface or pass entirely through the material (i.e.,the result of translucency). Light reflected from the surface may beeither reflected specularly (i.e., the angle of reflection equals theangle of incidence), or it may be reflected diffusely (i.e., light maybe reflected at any angle). When light is reflected from a specularsurface, the reflected light tends to be concentrated. When it isreflected from a diffuse surface, the light tends to be distributed overan entire solid hemisphere (assuming the surface is planar) (see, e.g.,FIGS. 21-22B). Accordingly, if the receivers of such embodiments measureonly diffusely reflected light, the light spectrum (integrated spectrumor gray scale) will be less than an instrument that measures both thespecular and diffusely reflected light. Instruments that measure boththe specular and diffuse components may be referred to as “specularincluded” instruments, while those that measure only the diffusecomponent may be referred to as “specular excluded.”

An instrument that can distinguish and quantify the degree of gloss orthe ratio of specular to diffusely reflected light, such as withembodiments previously described, may be utilized in accordance with thepresent invention to correct and/or normalize a measured color spectrumto that of a standardized surface of the same color, such as a purelydiffuse or Lambertian surface. As will be apparent to one of skill inthe art, this may be done, for example, by utilizing the glossmeasurement to reduce the value or luminance of the color spectrum (theoverall intensity of the spectrum) to that of the perfectly diffusematerial.

A material that is translucent, on the other hand, tends to lower theintensity of the color spectrum of light reflected from the surface ofthe material. Thus, when measuring the color of a translucent material,the measured spectrum may appear darker than a similar colored materialthat is opaque. With translucency measurements made as previouslydescribed, such translucency measurements may be used to adjust themeasured color spectrum to that of a similar colored material that isopaque. As will be understood, in accordance with the present inventionthe measured color spectrum may be adjusted, corrected or normalizedbased on such gloss and/or translucency data, with the resulting datautilized, for example, for prosthesis preparation or other industrialutilization as described elsewhere herein.

Additional aspects of the present invention relating to the output ofoptical properties to a dental laboratory for prosthesis preparationwill now be described. There are many methods for quantifying color,including CIELab notation, Munsell notation, shade tab values, etc.Typically, the color of a tooth is reported by a dentist to the lab inthe form of a shade tab value. The nomenclature of the shade tab or itsvalue is an arbitrary number assigned to a particular standardized shadeguide. Dentists typically obtain the shade tabs from shade tabsuppliers. The labs utilize the shade tabs values in porcelain recipesto obtain the final color of the dental prosthesis.

Unfortunately, however, there are variances in the color of shade tabs,and there are variances in the color of batches of dental prosthesisceramics or other materials. Thus, there are variances in theceramics/material recipes to obtain a final color of a tooth resultingin a prosthesis that does not match the neighboring teeth.

In accordance with the present invention, such problems may be addressedas follows. A dental lab may receive a new batch of ceramic materialsand produce a test batch of materials covering desired color,translucency and/or gloss range(s). The test materials may then bemeasured, with values assigned to the test materials. The values andassociated color, translucency and gloss and other optical propertiesmay then be saved and stored, including into the dental instruments thatthe lab services (such as by modem download). Thereafter, when a dentistmeasures the optical properties of a patient's tooth, the output valuesfor the optical properties may be reported to the lab in a formula thatis directly related, or more desirably correlated, to the materials thatthe lab will utilize in order to prepare the prosthesis. Additionally,such functionality may enable the use of “virtual shade guides” or toothdata for customizing or configuring the instrument for the particularapplication.

Still other aspects of the present invention will be described withreference to FIGS. 27 and 28, which illustrate a cordless embodiment ofthe present invention. Cordless unit 500 includes a housing on which ismounted display 502 for display of color/optical property data or statusor other information. Keypad 504 is provided to Input various commandsor information. Unit 500 also may be provided with control switch 510for initiating measurements or the like, along with speaker 512 foraudio feedback (such as previously described), wireless infrared serialtransceiver for wireless data transmission such as to an intelligentcharging stand (as hereinafter described) and/or to a host computer orthe like, battery compartment 516, serial port socket 518 (forconventional serial communications to an intelligent charging standand/or host computer, and/or battery recharging port 520. Unit 500includes probe 506, which in preferred embodiments may include removabletip 508 (such as previously described). Of course, unit 500 may containelements of the various embodiments as previously described herein.

Charging stand 526 preferably includes socket/holder 532 for holdingunit 500 while it is being recharged, and preferably includes a socketto connect to wired serial port 518, wireless IR serial transceiver 530,wired serial port 524 (such as an RS232 port) for connection to a hostcomputer (such as previously described), power cable 522 for providingexternal power to the system, and lamps 528 showing the charging stateof the battery and/or other status information or the like.

The system battery may be charged in charging stand 526 in aconventional manner. A charging indicator (such as lamps 528) may beused to provide an indication of the state of the internal battery. Unit500 may be removed from the stand, and an optical measurement may bemade by the dentist. If the dentist chooses, the optical measurement maybe read from display 502, and a prescription may be handwritten orotherwise prepared by the dentist. Alternately, the color/opticalcharacteristics data may be transmitted by wireless IR transceiver 514(or other cordless system such as RF) to a wireless transceiver, such astransceiver 530 of charging stand 526. The prescription may then beelectronically created based upon the color/optical characteristicsdata. The electronic prescription may be sent from serial port 524 to acomputer or modem or other communications channel to the dentallaboratory.

With reference to FIG. 29, additional aspects of the present inventionwill be discussed.

As is known, certain objects consist of an inner, generally opaquelayer, and an outer, generally translucent layer. As previouslydiscussed, light that is incident on a certain object generally can beaffected by the object in three ways. First, the light can be reflectedfrom the outer surface of the object, either diffusely or specularly.Second, the light can be internally scattered and absorbed by the objectstructures. Third, the light can be internally scattered and transmittedthrough the object structures and re-emerge from the surface of theobject. Traditionally, it was difficult, if not impossible, todistinguish light reflected from the surface of the object, whetherspecularly or diffusely, from light that has penetrated the object, beenscattered internally and re-emitted from the object. In accordance withthe present invention, however, a differentiation may be made betweenlight that is reflected from the surface of the object and light that isinternally scattered and re-emitted from the object.

As previously described, a critical height h_(c) occurs when a pair offiber optics serve to illuminate a surface or object and receive lightreflected from the surface or object. When the probe's distance from theobject's surface is greater than the critical height h_(c) the receiverfiber optic is receiving light that is both reflected from the object'ssurface and light that is internally scattered and re-emitted by theobject. When the distance of the probe is less than the critical heighth_(c), light that is reflected from the surface of the object no longercan be received by the received fiber optic. In general, the only lightthat can be accepted by the receiver fiber optic is light that haspenetrated outer layer 540 and is re-emitted by the object.

Most of the internal light reflection and absorption within a certainobject occurs at junction 542, which in general separates outer layer540 from inner layer 544. In accordance with the present invention, anapparatus and method may be provided for quantifying optical propertiessuch sub-surface structures, such as the color of junction 542, with orwithout comparison with data previously taken in order to facilitate theassessment or prediction of such structures.

Critical height h_(c) of the fiber optic probe such as previouslydescribed is a function of the fiber's numerical aperture and theseparation between the fibers. Thus, the critical height h_(c) of theprobe can be optimized based on the particular application. In addition,a probe may be constructed with multiple rings of receive fiber opticsand/or with multiple numerical aperture receiving fiber optics, therebyfacilitating assessment, etc., of outer layer thickness, surface gloss,etc.

By utilizing multiple rings of receiver fiber optics, a measurement ofthe approximate thickness of the outer layer may be made based on acomparison of the peak intensity above the object surface and ameasurement in contact with the object surface. A probe with multiplecritical heights will give different intensity levels when in contactwith the object surface, thereby producing data that may be indicativeof the degree of internal scattering and outer thickness or, objectmorphology at the point of contact, etc.

Accordingly, in accordance with the present invention, the color orother optical characteristics of a sub-surface structure, such asjunction 542 of an object, may be assessed or quantified in a mannerthat is in general independent of the optical characteristics of thesurface of the object, and do so non-invasively, and do so in a mannerthat may also assess the thickness of the outer layer 540.

Additionally, and to emphasize the wide utility and variability ofvarious of the inventive concepts and techniques disclosed herein, itshould be apparent to those skilled in the art in view of thedisclosures herein that the apparatus and methodology may be utilized tomeasure the optical properties of objects using other optical focusingand gathering elements, in addition to the fiber optics employed inpreferred embodiments herein. For example, lenses or mirrors or otheroptical elements may also be utilized to construct both the light sourceelement and the light receiver element. A flashlight or other commonlyavailable light source, as particular examples, may be utilized as thelight source element, and a common telescope with a photoreceiver may beutilized as the receiver element in a large scale embodiment of theinvention. Such refinements utilizing teachings provided herein areexpressly within the scope of the present invention.

As will be apparent to those skilled in the art, certain refinements maybe made in accordance with the present invention. For example, a centrallight source fiber optic is utilized in certain preferred embodiments,but other light source arrangements (such as a plurality of light sourcefibers, etc.). In addition, lookup tables are utilized for variousaspects of the present invention, but polynomial type calculations couldsimilarly be employed. Thus, although various preferred embodiments ofthe present invention have been disclosed for illustrative purposes,those skilled in the art will appreciate that various modifications,additions and/or substitutions are possible without departing from thescope and spirit of the present invention as disclosed in the claims. Inaddition, while various embodiments utilize light principally in thevisible light spectrum, the present invention is not necessarily limitedto all or part of such visible light spectrum, and may include radiantenergy not within such visible light spectrum.

With reference to FIG. 5A, the intensity measured by a single receiverfiber is shown as a function of time as a source fiber optic and areceiver fiber optic pair are moved into contact with an object and aremoved away from the object. FIG. 5A illustrates the intensity as afunction of time, however as will be apparent to one skilled in the art,the intensity detected by the receiver fiber can also be measured andplotted as a function of height. A given fiber optic pair of source andreceiver fiber optics, perpendicular to a surface (or at least at afixed angle relative to a surface) will exhibit a certain intensity vs.height relationship. That relationship generally is consistent forcertain materials of consistent gloss, color and translucency. Themathematical intensity vs. height relationship for certain source andreceiver fiber optic pairs can be calculated or measured and stored as alook up table value or as a polynomial or other mathematicalrelationship. What is important to note is that there is an intensitypeak that is a function of the gloss, translucency and color of theobject being measured. For similar materials, the intensity value at agiven height varies dependent upon color, although the shape of theintensity vs. height curve is largely independent of color. Thus, aswill be apparent to one skilled in the art, the present invention mayalso serve as a proximity sensor, determining height from the intensitymeasurements. The instrument is calibrated by moving it towards theobject until the peaking intensity is detected. While the instrumentmoves towards the object, the light intensities are rapidly measured andsaved in memory such as RAM 10 shown in FIG. 1. From the value of themeasured peaking intensity (utilized to normalize the intensity vs.height relationship of the fiber pair) the proximity sensor can becalibrated. Thereafter, the present invention may be utilized to measurethe height of the fiber optic pair from the surface of the objectwithout contacting the object.

The present invention may find application in a wide range of industrialactivities. Certain applications of the present invention include, butare not limited to, measuring the optical properties of teeth andutilizing the measurements as part of a patient data base and utilizingthe measurements for dental prosthesis preparation.

Another application of the present invention is its use in dermatologyin quantifying the optical properties including color of skin and othertissues and saving the measurements as part of a patient data baserecord and utilizing the measurements made over a period of time fordiagnostic purposes.

Yet another application of the present invention is in the foodpreparation industry where the color and other optical properties ofcertain foods that are affected by the preparation process are measuredand monitored with the disclosed invention and are utilized to determinewhether or not the food meets certain acceptance criteria and where themeasurements may be also utilized as part of a control and feed backprocess whereby the food is further processed until it is eitheraccepted or rejected. Similarly, in automated food processing, such asfor vegetables or fruit, measurements may be taken and an assessment orprediction of the condition of the vegetable or fruit made, such asripeness.

Yet another application of the present invention is to measure the colorand optical properties of objects newly painted as part of a controlprocess. For example, paint may be applied to the object, with theobject then measured to determine if a suitable amount or type of painthas been applied, perhaps with the process repeated until a measurementcorresponding to a desired surface condition is obtained, etc.

Yet another application of the present invention is to measure theoptical properties of newly painted objects over a period of time todiscern if the paint has cured or dried. Similarly, such an object maybe measured to determine if additional gloss coatings, surface texturefactors or fluorescence factors, etc., should be added to achieve a moreoptimum or desired object.

Yet another application of the present invention is, in an industrial orother control system, where items are color coded or have color or glossor translucency or combinations of optical properties that identify theobjects and where the optical properties are measured utilizing thedisclosed invention and are sorted according to their opticalproperties. In general, the present invention may be utilized to measurethe optical properties of objects in an industrial process flow, andthen compare such measurements with previously stored data in order tosort, categorize, or control the direction of movement of the object inthe industrial process.

Yet another application of the present invention is to place color codedor gloss coated or translucent tags or stickers on objects that serve asinventory control or routing control or other types of identification ofobjects in industrial processes.

Yet another application of the present invention is part of the printingprocess to measure and control the color or other optical properties ofinks or dies imprinted on materials. In such embodiments, implements asdescribed herein may be integrated into the printer or printingequipment, or used as a separate implement.

Yet another application of the present invention is part of thephotographic process to measure, monitor and control the opticalproperties of the photographic process. In such embodiments, implementsas described herein may be integrated into the camera or otherphotographic instrument, or used as a separate implement.

Yet another application of the present invention is to measure thedistance to the surface of objects without being placed into contactwith the object.

The present invention may be used in an industrial process in whichcoatings or material are added to or removed from an object. The objectmay be measured, and coatings or materials added or removed, with theobject remeasured and the process repeated until a desired object orother acceptance criteria are satisfied. In such processes, comparisonswith previously stored data may be used to assess whether the desiredobject is obtained or the acceptance criteria satisfied, etc.

In yet another application, the present invention is utilized in therestoration of paintings or other painted objects, such as art works,automobiles or other objects for which all or part may need to bepainted, with the applied paint matching certain existing paint or othercriteria. The present invention may be used to characterize whetherpaint to be applied will match the existing paint, etc. In suchprocesses, comparisons with previously stored data may be used to assesswhether the desired paint match will be obtained, etc.

In general, the present invention may find application in any industrialprocess in which an object or material may be measured for surfaceand/or subsurface optical characteristics, with the condition or statusof such object or material assessed or predicted based on suchmeasurements, possibly including comparisons with previously stored dataas previously described, etc. Additionally, and to emphasize the wideutility and variability of various of the inventive concepts andtechniques disclosed herein, it should be apparent to those skilled inthe art in view of the disclosures herein that the apparatus andmethodology may be utilized to measure the optical properties of objectsusing other optical focusing and gathering elements, in addition to thefiber optics employed in preferred embodiments herein. For example,lenses or mirrors or other optical elements may also be utilized toconstruct both the light source element and the light receiver element.A flashlight or other commonly available light source, as particularexamples, may be utilized as the light source element, and a commontelescope with a photoreceiver may be utilized as the receiver elementin a large scale embodiment of the invention. Such refinements utilizingteachings provided herein are expressly within the scope of the presentinvention.

In addition to the foregoing embodiments, features, applications anduses, other embodiments and refinements in accordance with the presentinvention will now be described. As with prior descriptions,descriptions to follow are without being bound by any particular theory,with the description provided for illustrative purposes.

A variety of devices may be used to measure and quantify the intensityof light, including, for example, photodiodes, charge coupled devices,silicon photo detectors, photomultiplier tubes and the like. In certainapplications it is desirable to measure light intensity over a broadband of light frequencies such as over the entire visible band. In otherapplications it is desirable to measure light intensities over narrowbands such as in spectroscopy applications. In yet other applications itis desirable to measure high light intensities such as in photographiclight meters. In still other applications it is desirable to measure lowlight intensities such as in abridged spectrometers. Typically whenmeasuring low light intensities, long sampling periods of the order ofone second or longer are required.

In accordance with other aspects of the present invention, a method andapparatus are disclosed that may be used to measure multiple lightinputs rapidly. Such an embodiment preferably utilizes a photodiodearray, such as the TSL230 manufactured by Texas Instruments, Inc., and agate array manufactured by Altera Corporation or Xilinx, Inc. In certainapplications, such an embodiment may be utilized to measure broad bandvisible and infra-red light. In other applications, such an embodimentmay be utilized as an abridged spectrometer in which each photodiodearray has a notch filter, such as an interference filter, positionedabove the light sensor.

The TSL230 consists of 100 silicon photodiodes arranged in a square 10by 10 array. The 100 photodiodes serve as an input to an integrator thatproduces an output signal of a frequency proportional to the intensityof light incident upon the array. The TSL230 has scale and sensitivityinputs allowing the sensitivity and scale to each be varied by a factorof 100, for a net range of 10⁴. The output frequency can vary from amaximum of approximately 300 k Hz (sensor is saturated) to sub Hzranges. Thus, the sensor can detect light inputs ranging over sevenorders of magnitude by varying the sensitivity and/or scale of thesensor and can detect light ranges of over five orders of magnitude at agiven setting.

In spectroscopy applications for such embodiments, each sensor ismounted with an optical filter such as an interference filter. As isknown in the art, interference filters have high out-of-band rejectionand high in-band transmission, and may be constructed with very narrowband pass properties. As an example, interference filters may beconstructed with band pass ranges of 20 nanometers or less. Inaccordance with certain aspects of the present invention, anabridged-type spectrometer may be constructed with TSL230 (or similar)sensors and interference filters that is suitable for reflectivity ortransmission spectrographic applications such as measuring the color ofobjects. In color determination applications it is not necessary todetect “line” spectra, but it often is desirable to have high gray scaleresolution, e.g., to be able to resolve the light intensity to 1 part in1000 or greater.

Instruments and methods for measuring the optical properties ofmaterials and objects have been previously described. Such an instrumentmay consist of a probe and an abridged spectrometer. The probe may bemoved into contact or near contact with the surface of the material orobject (by movement of the probe or material/object, etc.), and thespectrum of the light received by the probe was analyzed as the probewas moved towards the surface. Since the probe was not stationary,preferably numerous measurements are taken in succession, with thespectra dynamically taken and/or analyzed as the probe relatively movesin proximity with the object.

One difficulty that results from narrowing the band width of notch orinterference filters is that such narrowing reduces the light intensityincident upon each sensor. Thus, to measure low light levels, longsampling times typically are required. In the case of the TSL230 sensor,as the light level decreases, the output frequency of the devicedecreases. Thus, if it is desired to make 200 samples per second with anabridged spectrometer constructed with notch filters and TSL230s, oneneeds enough light to cause the TSL230 output to oscillate at a rate ofat least 200 Hz. Since the maximum range of the sensor is approximately300 k Hz, the maximum dynamic range of the sensor is reduced to (300 kHz)/(200 Hz) or roughly 1.5×10³. If the light inputs are low, then thedynamic range is reduced still further.

FIG. 30 illustrates an abridged visible light range spectrometer inaccordance with another embodiment of the present invention. Thisembodiment utilizes TSL230 sensors 616, a light source or lamp 604,preferably a hot mirror that reflects IR light with wavelengths above700 nanometers (not expressly shown in FIG. 30), fiber optic cableassembly consisting of one or more sources (illustrated by light path608) providing light to object 606, and one or more receivers(illustrated by light path 618) receiving light from object 606, gatearray 602 such as an Altera FLEX 10K30™ (believed to be a trademark ofAltera Corporation), which is coupled to computer 600 and receivessignal inputs from sensors 616 over bus 620. In one preferred embodimentup to fifteen or more TSL230 sensors are utilized. Each TSL230 sensor616 has an interference filter 614 positioned above the sensor, witheach filter preferably having a nominal bandwidth of 20 nanometers (orother bandwidth suitable for the particular application). Sensors 616also preferably receive a small and controlled amount of light (lightpath 610) directly from light source 604, preferably after IR filtering.The light source input to sensors 616 serves to bias sensors 616 toproduce an output of at least 200 Hz when no light is input to sensors616 from filters 614. Thus, sensors 616 will always produce an outputsignal frequency greater than or equal to the sampling frequency of thesystem. When input light intensities are small, the frequency change issmall, and when the light input is large, the frequency change will belarge. The scale and sensitivity of sensors 616 are set (by gate array602 over control bus 612, which may be under control of computer 600) todetect the entire range of light input values. In most cases,particularly in object color determination, the maximum amount of lightinput-into any one of sensors 616 is determined by light source 604 andfilters 614 and can be appropriately controlled.

Gate array 602 serves to measure the output frequency and period of eachof sensors 616 independently. This may be done by detecting whenever anoutput changes and both counting the number of changes per samplingperiod and storing the value of a high speed counter in a first registerthe first time an output changes, and storing the value in a secondregister for each subsequent change. The second register will thus holdthe final value of the timer. Both high to low and low to hightransitions preferably are detected. The output frequency (f) of eachsensor is thus: $\begin{matrix}{f = \frac{\left( {N - 1} \right)}{\left( {P_{h} - P_{l}} \right)}} & \left. 1 \right)\end{matrix}$where:

N=Number of transitions in sample period;

P₁=Initial timer count; and

P_(h)=Final timer count.

The internal high speed timer is reset at the start of each samplingperiod ensuring that the condition P_(h)>P₁ is always true.

The precision of a system in accordance with such an embodiment may bedetermined by the system timer clock frequency. If P_(r) is the desiredprecision and S_(r) is the sampling rate, then the frequency of thetimer clock is:f _(t) =P _(r) ·S _(r)  2)For example, for a sampling rate of 200 and a precision of 2¹⁶, thetimer clock frequency is 200×2¹⁶ or 13 MHz.

If the input light intensities are high, N will be a large number. Ifthe input light intensities are low, N will be small (but always greaterthan 2, with proper light biasing). In either case, however, P_(h)−P₁will be a large number and will always be on the order of ½ theprecision of the system. Thus, in accordance with such embodiments, thetheoretical precision to which the light intensities can be measured maybe the same for all sensors, independent of light input intensity. Ifone sensor has an output range of 200 to 205 Hz (very low light input),the intensities of light received by this sensor may be measured toabout the same precision as a sensor with 10,000 times more light input(range of 200 to 50,200 Hz). This aspect of such embodiments is veryunlike certain conventional light sensors, such as those utilizing ADCs,analog multiplexers and sample and hold amplifiers, where the precisionof the system is limited to the number of bits of the ADC available overthe input range. To provide for the wide input range in a system with anADC, a variable gain sample and hold amplifier typically is required. Itis also difficult for an ADC to sample to 16 bits accurately.

With such embodiments of the present invention, the absolute accuracygenerally is limited by the stability of the lamp and electrical noise,both of which may be reduced and in general are minimal because of thesimplicity of the design and the few components required on a circuitcard. A gate array, which may be field programmable or the like,typically may readily accommodate 20 or more TSL230 sensors and alsoprovide for an interface to a computer, microprocessor ormicrocontroller utilizing the light data. It also should be noted that,instead of a gate array, such embodiments may be implemented with highspeed RISC processors or by DSPs or other processing elements.

It should be noted that the use of light biasing, and other aspectsthereof, also are described elsewhere herein.

In addition to the foregoing embodiments, features, applications anduses, still other embodiments and refinements in accordance with thepresent invention will now be described.

Certain objects and materials such as gems and teeth exhibit reflectedlight spectrums that are a function of incident light angle andreflected light angle. Such objects and materials are sometimes referredto as opalescent materials. In accordance with other embodiments of thepresent invention, instruments and methodologies may be provided forspecifically measuring and/or quantifying the opalescent characteristicsof objects and materials, in addition to characteristics such as color,gloss, translucency and surface texture, it being understood thatpreviously described embodiments also may be used to capture spectraland other data (such as a plurality of spectrums), which can be comparedand/or processed to quantify such opalescent materials.

Such a further embodiment of the present invention is illustrated inFIG. 31. In accordance with this embodiment, light source 638 provideslight coupled through a light path (preferably light source fiber 636)to probe 630 through optical cable 632. Light received by the probe(i.e., returned from the object or material being evaluated) is coupledto spectrometer/light sensors 640 through a suitable light path(preferably one or more light receiver fibers from optical cable 632).Computer 642 is coupled to spectrometer/light sensors 640 by way ofcontrol/data bus 648. Computer 642 also is coupled to light source 638by way of control line(s) 646, which preferably control the on/offcondition of light source 638, and optionally may provide other controlinformation, analog or digital signal levels, etc., to light source 638as may be desired to optimally control the particular light chosen forlight source 638, and its particular characteristics, and for theparticular application. Light from light source 638 optionally may becoupled to spectrometer/light sensors 640 by light path 644, such as forpurposes of providing light bias (if required or desired for theparticular spectrometer chosen), or for monitoring the characteristicsof light source 638 (such as drift, temperature effects and the like).

Computer 642 may be a conventional computer such as a PC ormicrocontroller or other processing device, and preferably is coupled toa user interface (e.g., display, control switches, keyboard, etc.),which is generically illustrated in FIG. 31 by interface 652.Optionally, computer 642 is coupled to other computing devices; such asmay be used for data processing, manipulation, storage or furtherdisplay, through interface 650. Computer 642 preferably includes thetypical components such as (but not limited to) a CPU, random access orother memory, non-volatile memory/storage for storing program code, andmay include interfaces for the user such as display, audio generators,keyboard or keypad or touch screen or mouse or other user input device(which may be through interface 652), and optionally interfaces to othercomputers such as parallel or serial interfaces (which may be throughinterface 650). Computer 642 interfaces to spectrometer/light sensors640 for control of the spectrometer and overall system and to receivelight intensity and light spectrum data from spectrometer/light sensors640. In a preferred embodiment, control/data bus 648 for interfacing tospectrometer/light sensors 640 is a standard 25 pin bi-directionalparallel port. In certain embodiments, computer 642 may be separate,standalone and/or detachable from spectrometer/light sensors 640 and maybe a conventional laptop, notebook or other portable or handheld-typepersonal computer. In other embodiments, computer 642 may be an integralpart of the system contained in one or more enclosure(s), and may be anembedded personal computer or other type of integrated computer.Purposes of computer 642 preferably include controlling light source 638and spectrometer/light sensors 640, receiving light intensity andspectral or other data output from spectrometer/light sensors 640,analyzing received or other data and determining the optical propertiesof the object or material, and displaying or outputting data to a useror other computing device or data gathering system.

In a preferred embodiment, the output end of probe 630 may beconstructed as illustrated in FIG. 32. Numerous other probeconfigurations, including probe configurations as described elsewhereherein, may be used in such embodiments. In accordance with suchpreferred embodiments, optical characteristics determinationsystems/methods may be obtained that provide for a broader range ofmeasurement parameters, and, in certain applications, may be easier toconstruct. Probe cross section 656 includes central fiber optic 658,which is preferably surrounded by six perimeter fiber optics 660 and662. Central fiber optic 658 is supplied by light from the light source(such as light source 638). Six perimeter fiber optics 660 and 662 arelight receivers and pass to spectrometer/light sensors 640. In onepreferred embodiment, all seven fiber optics have the same numericalaperture (NA); however, as disclosed below, the numerical aperture ofthe light source and consequently the source fiber optic preferably canbe varied. Also, in certain embodiments the received cone of light fromcertain of the receiver fiber optics is also controlled and varied toeffectively vary the NA of certain receivers.

As illustrated in FIG. 32, central fiber optic 658 (S) serves as thelight source. Fiber optics 660 labeled 1, 3, 5 preferably are “wideband” fibers and pass to light sensors (preferably withinspectrometer/light sensors 640) that measure light intensity over anentire spectral range. The other three light receivers 662 labeled 2, 4,6 preferably are “dual” receivers and pass to both a spectrometer and to“wide band” light sensors (also preferably within spectrometer/lightsensors 640). As previously described, the probe in conjunction with aspectrometer, computer, light source and “wide band” light receivers canbe used to measure the color and translucency and surface properties ofteeth and other materials. Also as previously described, the probe witha combination of NA “wide band” receiver fiber optics can additionallybe utilized to measure the gloss or the degree of specular versusdiffuse light received from a surface.

FIG. 33A is a diagram of a preferred embodiment of spectrometer/lightsensors 640. In this embodiment, certain optical fibers from the probeare coupled to wide band light sensors (such sensors, which may includeTSL230 sensors and optics and/or filters as described elsewhere hereinare illustrated as sensors 676 in FIG. 33A), while other of the opticalfibers are coupled to both a spectrometer, in order to spectrallymeasure the light received by the probe, and to wide band light sensors.Fibers 660 (1,3,5) preferably are coupled to three wide band lightsensors (light path 682 of FIG. 33A). Preferably, the lightreceiving/sensing elements are Texas Instruments TSL230s, although theymay also be photo diodes, CCDs or other light sensors. Fibers 660(1,3,5) preferably are masked by iris 694 to reduce the size of the coneof light produced by the fiber as illustrated in FIG. 34. Mask or iris694 serves to limit the NA of the receiver by allowing only light rayswith a maximum angle of a to be received by the receiver light sensor.

If: h=height of end of fiber to iris

-   -   r=radius of opening of the iris    -   a=radius of the fiber        then: $\begin{matrix}        {\quad{\alpha = {{Tan}^{- 1}\left( \frac{r + a}{h} \right)}}} & \left. 1 \right)        \end{matrix}$        Hence, the effective NA of the receiver fiber optic can be        reduced and controlled with iris 694. By utilizing a variable        iris or an iris that is controlled with a servo such as those        utilized in conventional cameras, the NA of the receiver fiber        optic can be controlled by the system and can be varied to best        match the object or material being measured. Referring again to        FIG. 34, exemplary receiver fiber 690 provides light to        exemplary light sensor 676 through iris 694. Light rays such as        light rays 696A of a certain limited angle pass through iris        694, while other light rays within the acceptance angle of fiber        690 (the outer limit of the acceptance angle is illustrated by        dashed line 696 in FIG. 34) but not within the limited angular        range allowed by iris 694 are blocked, thereby enabling iris 694        to effectively emulate having a reduced or variable NA light        receiver.

Referring again to FIG. 33A, light source 638 may be coupled to certainof sensors 676 through light path 674. Light bias, such as previouslydescribed, may be provided from the light source, or alternatively, fromseparately provided LED 680, which may couple light to certain ofsensors 676 for providing controllable light bias to sensors 676 throughlight conduit 678. Control of LED 680 for providing controllable lightbias to certain of sensors 676, etc., is described elsewhere herein.Light from fibers 662 preferably are coupled (through light path 684 inFIG. 33A) to one or more diffusing cavities 686 (described in moredetail elsewhere herein), outputs of which are coupled to certain ofsensors 676 through light paths/conduits 688 as illustrated. Control ofsensors 676, and data output from sensors 676, preferably is achieved byway of gate array 670, which may be coupled to a computing device by wayof interface 668 (the use of gate array or similar processing elementand the use of such a computer device are described elsewhere herein).

The use of diffusing cavities 686 in such embodiments will now befurther described. As illustrated, certain of the light receivers 662(2, 4, 6) may be coupled to one or more diffusing cavities 686 throughlight path 684, which may serve to split the light receivers into, forexample, six (or more or fewer) fiber optics with a diffusing cavity asillustrated in FIGS. 35A, 35B, and 35C. One of light receivers 662 isthe central fiber in diffusing cavity 686 and is surrounded by six fiberoptics 702 as part of fiber optic bundle 698. Diffusing cavity 686serves to remove any radial or angular light distribution patterns thatmay be present in receiver fiber optic 662, and also serves to moreevenly illuminate the six surrounding fiber optics. Thus, lightreceivers 662 (2, 4, 6) illustrated in FIG. 32 may each be split intosix (or a different number) fibers resulting in eighteen receivers.Three of the eighteen fibers, one per diffusing cavity, preferably passto wide band sensors which may have iris 694 (see FIG. 34). The otherfifteen fibers preferably pass to a spectrometer system (such as part ofspectrometer/light sensors 640, which may consist of a plurality ofsensors 676, such as previously described). For the visible band,fifteen fiber optics and interference notch filters preferably are usedto provide a spectral resolution of: $\begin{matrix}{\frac{{700\quad{nm}} - {400\quad{nm}}}{15} = {20{{nm}.}}} & \left. 2 \right)\end{matrix}$A greater or lesser number of fibers and filters may be utilized inaccordance with such embodiments in order to increase or decrease thespectral resolution of the system/spectrometer.

In FIGS. 33B and 35C, an alternate embodiment of the present inventionutilizing a different arrangement of diffusing cavity 686 will now bedescribed. In such embodiments, three “dual band” receivers 662 are allpositioned in common fiber optic bundle 698 and one diffusing cavity 686is utilized. Fiber optic bundle 698 preferably contains three receiverfibers 662 and fifteen additional fibers 703 for the spectrometersystem, although greater or fewer fibers may be utilized in otherarrangements depending on the number of color sensors in the system. Incertain embodiments, fifteen fiber optics 703 in the bundle may be ofdifferent diameters to increase the efficiency of diffusing cavity 686and the cross sectional packing arrangement of the optical fibers infiber optic bundle 698. As an example of such preferred fiber bundlearrangements in accordance with such embodiments, larger diameter fibersmay be utilized for the color filters in the blue range of the visiblespectrum, where the light intensity from a tungsten-halogen lamp source638 is significantly less than in the red region of the visiblespectrum.

As described elsewhere herein, a spectrometer system may be constructedof Texas Instruments TSL230 light sensors, interference filters, lightbiasing elements and a gate array such an Altera FLEX 10K30 in order tocontrol the light sensors, interface to a computer via a parallel orother interface and to measure the frequency and period of the lightsensors simultaneously at a high rate in order to accurately and rapidlymeasure light spectrums and light intensities. Although suchspectrometer systems are used in preferred embodiments, otherspectrometers such as those utilizing, for example, CCDs withdiffraction gratings are utilized in other embodiments.

FIG. 36 illustrates a further refinement of aspects of aspectrometer-type system in accordance with the present invention. Afiber optic, such as one of the fifteen fibers from three diffusingcavities as described earlier, preferably pass to light sensor 710(which may be a TSL230 light sensor, as previously described) throughinterference filter 708. Interference filters such as interferencefilter 708 serve as notch filters passing light over a narrow bandwidthand rejecting light that is out of band. The bandwidth of the lighttransmitted through the filter, however, is dependent upon the angle ofincidence of the light on the filter, and in general is broadened as theangle of incidence increases. Since fiber optics produce a cone oflight, it has been determined that it is desirable to collimate the coneto reduce such bandwidth spreading. As illustrated in FIG. 36, the coneof light produced by exemplary fiber optic 704 (illustrated by lines712A) preferably is collimated with first aspheric lens (or fresnellens) 706A (illustrated by lines 712B) prior to entering interferencefilter 708. Light emitted from filter 708 (illustrated by lines 712C) is“gathered” by second aspheric lens (or fresnel lens) 706B to concentrate(illustrated by lines 712D) as much light as possible on light sensor710. In accordance with such embodiments, filters, particularlyinterference-type filters, may more optimally be utilized in a manner toreduce such bandwidth spreading or other undesirable effects.

Referring again to FIG. 33A (the discussion also is generally applicableto FIG. 33B), light biasing as previously described will be discussed ingreater detail. As previously described, in order to rapidly sampleTSL230-type sensors, the sensors may require light biasing. Withoutlight biasing, depending upon the light intensity presented to theparticular sensors, a TSL230 sensor may not produce an output changepair of transitions (e.g., high to low and low to high transitions, orlow to high and high to low transitions) during the sampling period,hence a light intensity measurement may not be possible for that sensor.In preferred embodiments, the sensing system detects both high to lowand low to high transitions and requires at minimum two transitions tomake a measurement. In other words, such system measures half periods.For example, assume that as the light intensity on a particular TSL230decreases such that its output frequency decreases from 201 Hz to 199Hz. At 201 Hz, the output of the TSL230 transitions with a period of{fraction (1/201)} sec or every 4.975 ms. At 199 Hz, the outputtransition period is {fraction (1/199)} sec or 5.025 ms. If the samplingrate is 200 samples per second, then the sampling period is 5.00 ms.Thus, if the TSL230 transitions every 4.975 ms, the sensing system willalways detect either two or three transitions and will always be able tomake an intensity measurement. At 199 Hz, however, the detectioncircuitry will detect either one or two transitions. As a result, duringcertain sampling intervals, measurements are possible, while duringother intervals measurements are not possible, thereby resulting inmeasurement discontinuities even though the light intensity has notchanged.

It is desirable to measure light over a broad range of intensity valuesat high rates including very low light intensities. By utilizing lightbiasing of the TSL230 sensors as illustrated in FIG. 33A, the minimaloutput frequency of the TSL230s can be controlled. The minimal lightvalue preferably is measured as part of a normalization or calibrationprocedure as follows.

-   1. The light bias is turned on and allowed to stabilize.-   2. The probe is placed into a black enclosure. A “black level”    intensity measurement I_(b) is made and recorded for each sensor,    preferably in a simultaneous manner.-   3. The light source is turned on and allowed to stabilize. A “white    level” intensity measurement I_(w) is made and recorded for each    sensor, again preferably in a simultaneous manner, on a “white”    standard such as barium sulfide or on “Spectralon,” believed to be a    trademarked product of Labsphere, Inc. The actual intensities    measured by all sensors will vary from the standard values I_(s).    Typically in color measurements the standard value I_(s) is    nominally “100%.”-   4. Subsequent light measurements may be normalized by subtracting    the “black level” intensity and by adjusting the gain from the white    level measurement resulting in a normalized intensity I_(N) for each    sensor as follows: $\begin{matrix}    {\quad{I_{N} = {\frac{I_{s}}{I_{w} - I_{b}}\left( {I - I_{b}} \right)}}} & \left. 3 \right)    \end{matrix}$    where I=Intensity measurement and I_(N) is the normalized or    calibrated intensity measurement. It should be noted that in such    preferred embodiments the normalization is made for each light    sensor, and independent “black level” and “white level” intensities    are saved for each sensor.

In certain situations, a long time may be required for the light sourceand for the light bias source to stabilize. In other situations, thelight source and bias source may drift. In preferred embodiments, thelight source is a 18 W, 3300 K halogen stabilized tungsten filament lampmanufactured by Welch Allyn, Inc. The light bias preferably is providedby a high intensity LED and a fiber optic light guide or conduit (seeLED 680 and light conduit 678 of FIG. 33A) that passes to each biasedsensor of sensors 676. The intensity of LED 680 preferably is controlledand varied with high frequency pulse width modulation, or by analogconstant current controllers. By controlling the intensity of bias LED680, the bias light level can be varied to best match the sensorsampling rate.

Preferably, one sensor, such as a TSL230 sensor, is provided to measurethe intensity of LED 680 and to correct for intensity variations of theLED light biasing system. Since LED 680 is monochromatic, one sensortypically is sufficient to track and correct for bias LED intensitydrift. The LED bias intensity preferably is measured and recorded whenthe “black level” measurement is made. For each subsequent lightintensity measurement, the black level for each sensor is corrected forLED drift as follows: $\begin{matrix}{{I_{b}({Corrected})} = {I_{b}\frac{I({BiasSensor})}{I_{b}({BiasSensor})}}} & \left. 4 \right)\end{matrix}$where: I(BiasSensor) is the intensity measured by the bias sensor,I_(b)(BiasSensor) is the “black level” intensity measured by the biassensor, I_(b) is the “black level” intensity measured by a light sensor(other than the bias sensor) and I_(b)(Corrected) is the adjusted biasused in equation 4) above.

Light source drift preferably is measured by a plurality of lightsensors. Since the light source is polychromatic light, its spectrum mayalso drift. It is understood that tungsten filament lamps producespectrums that are very nearly approximated by the spectrums of blackbody radiators and can be represented by the Planck law for black bodyradiators. $\begin{matrix}{{I(\lambda)} = {\left( \frac{2 \cdot \pi \cdot h \cdot c \cdot}{\lambda^{3}} \right)\left( \frac{1}{e^{\frac{hc}{hT\lambda}} - 1} \right)}} & \left. 5 \right)\end{matrix}$The only variable affecting the intensity of a black body radiator atany wavelength within the visible band is the temperature (T) of thesource. Thus, a single narrow band light sensor may be utilized todetect temperature variations of such a source. Additional factors,however, may affect the spectral output of the lamp, such as depositingof the filament on the lamp envelope or adjusting the spectrum of thelamp as described below. In the preferred embodiment, for more accuratespectral corrections and intensity variations of the lamp, additionalnarrow band filters are utilized. In certain of such preferredembodiments, three band pass filters and sensors are utilized to measurethe spectral shift and intensity of the lamp in a continuous manner, andsuch filters and sensors preferrably are further utilized to correct forlamp spectral and intensity drift.

FIG. 37 illustrates a preferred embodiment of a light source used inpreferred embodiments of the present invention. Such a light sourcepreferably consists of halogen tungsten filament lamp 724, with a lensmolded into the envelope of the lamp that produces a concentrated lightpattern on an axis parallel to the body of lamp 724. The use of such alens in lamp 724 is to concentrate the light output and to reduce theshadowing of the lamp filament that may result from lamps withreflectors. Hot mirror 722, which preferably is a “0° hot mirror,”reduces the intensity of IR light input into the system. In certainembodiments, the hot mirror may also contain color correctionproperties, for example, reducing light intensity for longer (red)wavelengths more than for shorter (blue) wavelengths. Light output fromlamp 724 passes through hot mirror 722 preferably to tapered glass rod720. The end of glass rod 720 nearest lamp 724 preferably has a diameternominally the diameter of the envelope of lamp 724. The other end ofglass rod 720 preferably is nominally 4 mm, or up to four times or morethe diameter of source fiber optic 714.

Glass rod 720 serves a number of purposes. First, glass rod 720 servesas a heat shield for fiber optic 714 by allowing fiber optic 714 to bedisplaced from lamp 724, with fiber optic 714 being thermally insulatedfrom lamp 724 by the existence of glass rod 720. Second, glass rod 720serves to concentrate the light over a smaller area near fiber optic 714and to broaden the angular distribution of light emerging from thenarrow end to provide a distributed light pattern that can uniformly“fill” the NA of source fiber optic 714. Without tapered glass rod 720,the angular distribution pattern of light emerging from lamp 724 may notentirely or evenly fill the acceptance cone of source fiber optic 714.To ensure that source fiber optic 714 is desirably filled with lightwithout an implement such as glass rod 720 would require source fiberoptic 714 to be very close to lamp 724, thereby creating a risk thatsource fiber optic 714 will overheat and possibly melt.

Between source fiber optic 714 and glass rod 720 preferably is iris 718.Iris 718 preferably is utilized to limit the angular range of light raysentering source fiber optic 714. When iris 718 is fully open, the entireacceptance cone of source fiber optic 714 may be filled. As iris 718 isclosed, the cone of light incident upon source fiber optic 714 isreduced, and hence the angular distribution of light incident upon fiberoptic 714 is reduced. As iris 718 is reduced further, it is possible toproduce a nearly collimated beam of light incident upon fiber optic 714.

It is understood that a property of fiber optics whose ends are highlypolished perpendicular to the axis of the fiber optic is that the angleof light incident on one end of the fiber optic is preserved as it exitsthe other end of the fiber optic. As is known to those skilled in theart, numerous technologies exist for polishing fiber optic cables. Thus,with a highly polished fiber optic, by varying the diameter of iris 718,the cone of light entering source fiber optic 714 can be controlled, andthus the cone of light emerging from source fiber optic 714 can becontrolled.

In an alternate embodiment, iris 718 is replaced by disk 730, whichpreferably includes a pattern of holes positioned near its perimeter asillustrated in FIGS. 38A and 38B. Preferably, disk 730 is driven withstepping motor 738 through gear 736 and gear teeth 730A so that disk 730may be rapidly moved to a desired position and held it in a stableposition in order to make a light measurement. Stepping motor 738 iscontrolled by a computer (such as described elsewhere herein; see, e.g.,FIGS. 30 and 31), which controls disk 730 to rotate about axis 732 andstop in a desired and controllable position. Thus, such a computer ineffect can vary the NA of the light source synchronously to eachmeasurement. The procedure preferably progresses as follows.

-   1. Rotate the disk to the desired aperture.-   2. Pause to allow the disk to stabilize.-   3. Measure one light sample.-   4. Rotate the disk to the next desired aperture and repeat the    process as required.

As illustrated FIG. 38B, the pattern of holes on disk 730 may be roundor any other desired shape. Such apertures also may constitute a patternof microscopic holes distributed to affect the light pattern of light orspectrum of light entering the source fiber. Additionally, the disk maycontain filters or diffraction gratings or the like to affect thespectrum of the light entering the source fiber. Such holes or aperturesalso may consist of rings that produce cones of light where the lightrays entering the fiber are distributed over a narrow or otherdesiredrange of angles. With the disk embodiment of FIGS. 38A and 38B,it is possible to control the light pattern of source fiber optic 714effectively over a wide range of angles.

Referring again to FIG. 37, light conduit 716 passes light such asthrough light path 674 to sensors 676 (see, e.g., FIGS. 33A and 33B) formeasuring the spectral properties of the lamp as described earlier. Ifthe iris or aperture disk controlling the distribution of light enteringsource fiber optic 714 modifies the spectral properties of the lightsource, then the resulting spectrum can be adjusted as describedearlier.

When a pair of fiber optics is utilized as described herein where onefiber serves as a light source and another fiber serves as a lightreceiver, the intensity of light received by the receiver fiber varieswith the height of the pair above the surface of the object or materialand also with the angle of the pair relative to the surface of theobject or material. As described earlier, in certain preferredembodiments the angle of the probe relative to the surface may bedetected by utilizing three or more fiber optic receivers having thesame receiver NA. After normalization of the system, if the intensitiesof the three receiver fibers (such as fibers 660 (1, 3, 5) in FIG. 32)are the same, then this is an indication that the probe is perpendicularto the surface. If the intensities vary between the three sensors, thenthis is an indication that the probe is not perpendicular to thesurface. As a general statement, this phenomenon occurs at all heights.In general, the intensity variation of the three fibers is dependentupon the geometry of the three fibers in the probe and is independent ofthe color of the material. Thus, as the probe is tilted towards fiber 1,for example, the intensities measured by sensors 3 and 5 will benominally equal, but the intensity measured by fiber 1 will vary fromfibers 3 and 5. As a result, the system can detect an angular shifttowards fiber 1. In preferred embodiments, by comparing the intensityvalues of fiber 1 to fibers 3 and 5, a measurement of the angle can bemade and the intensity of fibers 1, 3 and 5 can be corrected by acorrection or gain factor to “adjust” its light measurement tocompensate for the angular shift of the probe. It is thus possible withthe probe arrangement illustrated in FIG. 32 to detect and measureangular changes.

Angular changes also will affect the intensities measured by the otherfibers 662 (2, 4, 6). In a similar manner, the difference between the“wide band” sensors in fibers 662 (2, 4, 6) can also be utilized tofurther quantify the angle of the probe and can be utilized to adjustthe light intensity measurements. It should be noted, however, that theintensity shift due to angle of the probe affects the fibersdifferently. If sensors 662 (2, 4, 6) are utilized in the spectrometerillustrated in FIG. 33A, the intensity adjustment must be madeindependently for each fiber and for the set of six fibers emerging fromdiffusing cavity 686 illustrated in FIG. 35A. However, if one diffusingcavity 686 is utilized as illustrated in FIG. 33B, the angle correctionapplies to all sensors supplied by light paths 703 equally. With such anembodiment as illustrated in FIG. 33B, angle determination and/orcorrection may be made in a manner more desirable for some applications.

As the probe approaches the surface of an object or material (the probemay be moved towards the material or the material may be moved towardsthe probe), the source fiber illuminates the object/material. Some lightmay reflect from the surface of the object/material, and some light maypenetrate the object/material (if it is translucent or has a translucentlayer on its surface) and re-emerge from the material and may strike thereceiver fiber optic. As described elsewhere herein, the intensitymeasured by the receiver exhibits a peaking phenomenon where the lightintensity varies to a maximum value, and then falls until the probe isin contact with the object/material where it exhibits a minimum. If theobject/material is opaque, then the light intensity at the minimum isessentially zero. If the object/material is highly translucent, then theintensity may be near the peaking intensity.

Based on such phenomena, in accordance with other aspects of the presentinvention, it is possible to quantify the height of the probe and toadjust for height variations of the probe near the peaking height bymeasuring the peaking height intensity of the “wide band” sensors andcomparing the intensity value at other heights and adjusting the gain ofall sensors by the ratio of the measured intensity to the peakingintensity. If I_(p) is the peak intensity of a wide band receiver, andI_(m) is the intensity measured when the probe is in contact with thematerial, and I is the intensity measured at a height less than thepeaking height then the ratio: $\begin{matrix}{G = \frac{I_{p} - I_{m}}{I - I_{m}}} & \left. 6 \right)\end{matrix}$is the gain adjustment factor. If the gain adjustment factor is appliedto the spectrometer sensors, then the spectrum may be measuredindependent of height for a wide range of heights within the peakingheight.

Reference should now be made to FIGS. 39A and 39B. As a fiber optic pair(e.g., source fiber optic 742 and receiver fiber optic 744) approach amaterial or object 746, material or object 746 is illuminated by sourcefiber optic 742 (see, e.g., lines 745 of FIG. 39A). The light emittedfrom source fiber optic 742 may be controlled as described elsewhereherein. Thus, source fiber optic 742 can be controlled so as toilluminate material or object 746 with nearly collimated light (smallincident angles), or source fiber optic 742 can be controlled toilluminate material or object 746 with wide incident angles, or with apattern of angles or with different spectral properties. If source fiberoptic 742 is illuminated with an aperture disk with a slit pattern asillustrated in FIG. 38B, then source fiber optic 742 may be used toilluminate material or object 746 with a narrow singular range ofangles.

Consider source fiber optic 742 and receiver fiber optic 744 with thesame NA as illustrated in FIGS. 39A and 39B. The angular distribution oflight provided by source fiber optic 742 is dependent upon the sourcefiber only (and the angle of the probe) and is independent of the heightof the fiber from the material. If the probe is held substantiallyperpendicular to material or object 746, the angular distribution oflight is independent of height. The area illuminated by source fiber742, however, is height dependent and increases with increasing height.Receiver fiber optic 744 can only receive light that is within itsacceptance angle, thus it can only detect light reflected from thesurface that is reflected from the area of overlap of the two conesillustrated in FIGS. 39A and 39B.

FIG. 39A illustrates the fiber pair at the peaking height, while FIG.39B illustrates the fiber pair at the critical height. At the criticalheight, the only light reflecting from the surface that can be receivedby receiver fiber 744 is the source ray 745 and the reflected ray 748with angle of incidence equal to angle of reflection, or it can onlydetect “spectrally” reflected light. When the probe is at the peakingheight, however, the reflected light rays that can be received by thereceiver fiber vary over both a wider angle of incidence range and widerangle of reflection range. Thus, at the peaking height, the receiver isdetecting a broad range of incident angle light rays and reflected anglelight rays. By adjusting the spectrum for height shifts as describedabove and by detecting the angle of the probe relative to the surface ofthe material or object, the reflected or returned spectrum can bemeasured over a wide incident angular range and reflected angular range.

In general, for opaque surfaces, diffuse or specular, the heightadjusted spectrum will appear constant as the probe approaches thematerial or object. In general, for opalescent materials or objects,i.e., materials with a translucent surface in which light rays maypenetrate the material and be re-emitted, the height adjusted spectrumwill shift as the probe approaches the material or object. In general,for translucent materials such as teeth or gem stones, the spectrum willfurther shift when the probe is less than the critical height and incontact or near contact with the material or object.

As a further refinement to certain aspect of the present invention, theiris illustrated in FIG. 37 or the aperture disk illustrated in FIGS.38A and 38B may be utilized. In one such embodiment, the NA of sourcefiber optic 714 is held constant as the probe approaches the material orobject, and light intensity and spectrum measurements are made and savedin a data queue as described earlier. When the probe is in contact withthe material or object, the NA of source fiber optic 714 is changed(either from narrow to wide or from wide to narrow, depending upon thestate of the first set of measurements), and spectral measurements aremade as a function of source NA. The probe is then moved away from thematerial and light intensity and spectral measurements are made as thedistance from the probe increases and as the probe passes through thepeaking height. The spectral shift that occurs as a result of thevariance of the source NA and height preferably is used to quantify theopalescence of the material or object.

In an alternate embodiment, the aperture disk illustrated in FIGS. 38Aand 38B is rotated by stepping motor 738 synchronously to measuring thelight and spectral data as the probe is moved into proximity to thematerial or object or into contact with the material or object. Inanother alternate embodiment, the probe is positioned at a fixed heightfrom the material or in contact with the material or object and the NAof the source fiber is varied as light intensity and spectral data aremeasured. In yet another alternate embodiment, both the source andreceiver fiber NAs are varied as described earlier, and the resultingspectra are utilized to quantify the optical properties of the material.

An alternative embodiment of the present invention for quantifying thedegree of gloss of a material will now be described with reference toFIGS. 40A and 40B. FIGS. 40A and 40B illustrate source (742) andreceiver (744) fiber pair positioned above a highly specular surfacesuch as a mirror (FIG. 40A) and above a diffuse surface (FIG. 40B). Thecone of light from source fiber optic 742 is illustrated by circle 742A,and the acceptance cone of receiver fiber optic 744 is illustrated bycircle 744A, with the overlap illustrated by area 750. On a specularsurface, the only light that will be received by receiver fiber optic744 are the light rays whose angle of reflection equal the angle ofincidence, thus the only light rays striking the surface of receiver 744are the light rays striking the small circular area the size of thediameter of the fiber optics as illustrated by circle 752 in FIG. 40A.As long as receiver fiber optic 744 has an NA greater than source fiberoptic 742, all light incident upon receiver fiber optic 744 will beaccepted. Thus, the angular distribution of received light rays inreceiver fiber optic 744 is limited to a very narrow range and isdependent upon the height of the fiber optic pair from the surface.

Consider FIG. 40B, which illustrates a fiber optic pair positioned abovea diffuse surface. Any light ray incident upon the area of overlap ofthe two cones can be received by receiver fiber optic 744 (provided ofcourse that it is incident upon the receiver fiber). Thus, for diffusesurfaces, the angular distribution of light rays received by receiverfiber optic 744 is also height dependent, but is greater than theangular distribution for a specular surface. In accordance with suchembodiments of the present invention, such angular distributionvariation may be used to quantify optical properties such as gloss for aparticular material or object.

A detector in accordance with other embodiments of the present inventionis illustrated in FIG. 41, where single receiver fiber 758 is positionedabove a radial distribution of sensors (illustrated by sensors 760A and760B). Two or more sensors may be utilized, in one or two dimensions,although only two sensors are illustrated in FIG. 41 for discussionpurposes. In the illustrated embodiment, one sensor (sensor 760B) ispositioned corresponding to the center of fiber 758 and measures anglesnear zero, and the other sensor (sensor 760A) is positioned atapproximately ½ the acceptance angle of receiver fiber 758. In alternateembodiments, the sensors may be arranged or configured in a linear arraysuch as a CCD, or a two dimensional sensor such as a video camera CCD orMOS sensor. In accordance with aspects of the present invention, byanalyzing the intensity patterns of the sensors, the degree of gloss ofthe material may be measured and quantified.

As the probe is moved towards the material or object, the angulardistribution of light received by receiver fiber 758 changes dependentupon the surface of the material or object as illustrated in FIGS. 42Aand 42B. FIG. 42A illustrates the intensity pattern for the two sensorsfor a specular surface, and FIG. 42B shows the intensity pattern for adiffuse surface. Specular materials in general will tend to exhibit apeaking pattern where the peaking intensity of sensor 1 is much largerthan the peaking intensity of sensor 2. For diffuse materials thepeaking intensity of sensor 2 (wide angles) is closer to the peakingintensity of sensor 1. By quantifying the variation in peaking intensitythe degree of gloss of the material can be additionally quantified. Inaddition, in alternative embodiments, the relative values of the sensorsat a time when one or the other sensors is peaking are captured andfurther used to quantify the optical properties of the material orobject.

In conjunction with various of the foregoing embodiments, a variety ofoptic fibers may be utilized, with smaller fibers being used to assessoptical characteristics of smaller spots on the object or material underevaluation. In accordance with such aspects of the present invention andwith various of the embodiments described herein, fibers of about 300microns in diameter, and up to or less than about 1 millimeter indiameter, and from about 1 to 1.5 millimeters have been utilized,although fibers of other diameters also are utilized in otherembodiments and applications of the present invention. With such fibers,the optical properties of the object or materials under evaluation maybe determined with a spot size of about 300 microns, or alternativelyabout 1 millimeter, or about 1.5 millimeters, or from about 0.3 to 1millimeters, or from about 1 to 1.5 millimeters. In accordance with suchembodiments, optical properties of such a spot size, including spectral,translucence, opalescence, gloss, surface texture, fluorescence,Rayleigh scattering, etc., may be quantified or determined, including bydetermining a plurality of spectrums as the probe is directed towards orin contact or near contact with the object or material and possiblechanges in such spectrums, all with an instrument that is simplydirected towards a single surface of the object or material underevaluation.

It also should be noted that, in accordance with various principles ofthe various embodiments of the present invention described herein,refinements may be made within the scope of the present invention.Variations of source/receiver combinations may be utilized in accordancewith certain embodiments of the present invention, and various opticalproperties may be determined in accordance with the various spectraobtained with the present invention, which may include spectra taken atone or more distances from the object or material (and includingspectrally reflected light), and spectra taken at or near the surface(e.g., within the critical height, and substantially or wholly excludingspectrally reflected light). In certain embodiments, measurements may betaken in a manner to produce what is sometimes considered a goniometricmeasurement or assessment of the object or material under evaluation. Inother embodiments, features may sometimes be used with or withoutcertain features. For example, certain applications of aspects of thepresent invention may utilize perimeter fibers for height/angledetermination or correction, while other applications may not. Suchrefinements, alternatives and specific examples are within the scope ofthe various embodiments of the present invention.

Reference is made to copending application filed on even date herewithfor Apparatus and Method for Measuring Optical Characteristics of Teeth,and for Method and Apparatus for Detecting and PreventingCounterfeiting, both by the inventors hereof, which are herebyincorporated by reference.

Additionally, it should be noted that the implements and methodologiesmay be applied to a wide variety of objects and materials, illustrativeexamples of which are described elsewhere herein and/or in theco-pending applications referenced above. Still additionally,embodiments and aspects of the present invention may be applied tocharacterizing gems or precious stones, minerals or other objects suchas diamonds, pearls, rubies, sapphires, emeralds, opals, amethyst,corals, and other precious materials. Such gems may be characterized byoptical properties (as described elsewhere herein) relating to thesurface and/or subsurface characteristics of the object or material. Asillustrative examples, such gems may be characterized as part of a buy,sell or other transaction involving the gem, or as part of a valuationassessment for such a transaction or for insurance purposes or the like,and such gems may be measured on subsequent occasions to indicatewhether gem has surface contamination or has changed in some respect orif the gem is the same as a previously measured gem, etc. Measuring agem or other object or material in accordance with the present inventionmay be used to provide a unique “fingerprint” or set of characteristicsor identification for the gem, object or material, thereby enablingsubsequent measurements to identify, or confirm the identity ornon-identity of, a subsequently measured gem, object or material.

It also should be noted that the implements and methodologies describedin the co-pending applications referenced above also may be applied toembodiments and features of the present invention as described herein,including, for example, material mixing or preparation, remotetransmission of optical characteristics data and remote or localcreation of a second object or material based thereon (which may beremotely measured with a second instrument, etc.), audio feedback ofvarious types to add operator use, integration with cameras or otherimplements, posturization or sectoring of an object to be measured withthe object measured multiple times and/or in multiple locations, datacapture, storage and manipulation in software databases, computers andthe like. All such refinements, enhancements and further uses of thepresent invention are within the scope of the present invention.

1. A method for determining color information from light received by asensing element, comprising the steps of: coupling the light to thesensing element, wherein the sensing element comprises a plurality ofphotodiodes, wherein a first set of photodiodes receive light thatpassed through a first filter that passes light of a first band ofwavelengths, wherein a second set of photodiodes receive light thatpassed through a second filter that passes light of a second ban ofwavelengths, wherein a third set of photodiodes receive light thatpassed through a third filter that passes light of a third band ofwavelengths, wherein the sets of photodiodes are coupled to anintegrator and output a plurality of signals that each have a frequencyproportional to the intensity of light received by the respective set ofphotodiodes; coupling the plurality of signals to a processing element;determining color information with the processing element, wherein theprocessing element determines the color information based on theplurality of signals; and controlling the sensing element with controlsignals from the processing element, wherein a scale and sensitivity ofthe sensing element for the sets of photodiodes are controlled based ona range of light intensity values received by the sets of photodiodes.2. The method of claim 1, wherein the first, second and third filterscomprise bandpass filters.
 3. The method of claim 2, wherein the first,second and third filters comprise interference filters.
 4. The method ofclaim 1, wherein the plurality of signals are coupled to the processingelement without an analog-to-digital converter, wherein the processingelement comprises a gate array, microprocessor or digital signalprocessor.
 5. The method of claim 1, wherein bias light is provided tothe sets of photodiodes, wherein the frequency of the output signals isgreater than a minimum value.
 6. The method of claim 1, wherein a fourthset first set of photodiodes receive light over a wideband ofwavelengths.
 7. The method of claim 1, wherein the processing elementdetermines the frequency of each of the plurality of output signals. 8.The method of claim 1, wherein the processing element determines aperiod of each of the plurality of output signals.
 9. The method ofclaim 1, wherein the processing element determines the frequency and aperiod of each of the plurality of output signals.
 10. The method ofclaim 1, wherein the sensing element and the processing element areintegral to a portable, handheld color measurement system.
 11. A methodfor determining color information from light received by a sensingelement, comprising the steps of: coupling the light to the sensingelement, wherein the sensing element comprises a plurality ofphotodiodes, wherein a first set of photodiodes receive light thatpassed through a first filter that passes light of a first band ofwavelengths, wherein a second set of photodiodes receive light thatpassed through a second filter that passes light of a second ban ofwavelengths, wherein a third set of photodiodes receive light thatpassed through a third filter that passes light of a third band ofwavelengths, wherein the sets of photodiodes are coupled to anintegrator and output a plurality of signals that each have a frequencyproportional to the intensity of light received by the respective set ofphotodiodes; coupling the plurality of signals to a processing element;and determining color information with the processing element, whereinthe processing element determines the color information based on theplurality of signals; wherein the intensity of light is determined ineach of the first, second an third bands of wavelengths with a precisionthat is substantially independent of light input intensity value. 12.The method of claim 11, wherein the first, second and third filterscomprise bandpass filters.
 13. The method of claim 12, wherein thefirst, second and third filters comprise interference filters.
 14. Themethod of claim 11, wherein the plurality of signals are coupled to theprocessing element without an analog-to-digital converter, wherein theprocessing element comprises a gate array, microprocessor or digitalsignal processor.
 15. The method of claim 11, wherein bias light isprovided to the sets of photodiodes, wherein the frequency of the outputsignals is greater than a minimum value.
 16. The method of claim 11,wherein a fourth set first set of photodiodes receive light over awideband of wavelengths.
 17. The method of claim 11, wherein theprocessing element determines the frequency of each of the plurality ofoutput signals.
 18. The method of claim 11, wherein the processingelement determines a period of each of the plurality of output signals.19. The method of claim 11, wherein the processing element determinesthe frequency and a period of each of the plurality of output signals.20. The method of claim 11, wherein the sensing element and theprocessing element are integral to a portable, handheld colormeasurement system.